[Gavin10]

I met a wonderful woman and we both fell in love, it seems.
She expressed feelings about being very happy, never feeling so comfortable with someone and adoring us being together.
For six months this continued.
Until days before she broke up she continued like this and I was hugely in love too.
Whilst away for a week, for the three days before I returned she was overwhelmed on the phone and couldn't speak without being hugely upset.
Something was wrong. I suggested I give our weekend a miss, although I didn't know why. She insisted on meeting.
When I arrived, she was a different person. She wanted to talk but couldn't talk without being overwhelmed. Eventually, I hear messages along the lines of the pace of our relationship, her need to worry about her son...this was sudden and new and didn't make sense. I departed from our meeting feeling frustrated and confused.
I called later and heard that there was an ex intervening in her life. Eventually she said she thought "I was the one" but "there was a possibility" (elsewhere). She said she didn't want any regrets; it was so "close". She was extremely upset. I couldn't reconcile here feelings and statements throughout the relationship with this information. The sudden crisis. Also, it turns out she had left the other person due to a trust problem, seemingly he had been with someone else, and my girlfriend had just left, with no further contact. Before meeting me some months later.
Our relationship was deep, compelling and passionate.
I am cut off now. That's it.
I knew she had deep rooted fears arising from a previous marriage where she was traumatised. This affected here somewhat. One of them was being left alone, another was aggression. In our last conversation she made reference to this but that I had no characteristics like this but that she still didn't want to have regrets. I asked if she was making a choice and why didn't she simply withdraw without the trauma. She said she just didn't know until the previous two days (and admitted that her ex had turned up looking for her). She said she still didn't know: thought I was the one but thought also there was a "possibility" with this other person. Her state was such that she couldn't be capable of simply entering another relationship.
I asked for my things to be sent to me from her house which she was reluctant to do but eventually did.
I'm very confused and very hurt. On one level might it be a simple case of me being the rebound person and she needed to express powerful and deep feelings (for someone) for a while. But they were so genuine. On another level I sense there is something else afoot. Her grief was immense. But she has held through and maintained no contact now for two weeks. I just wrote her a note and acknowledged her dilemma and expressed how my feelings were pure. I returned a note she left me within which she said she loved me very much (days previously) and were the "best couple".
Extremely confused. Please help!

Reads like the stereotypical borderline relationship.

How a Borderline Personality Disorder Love Relationship Evolves - Roger Melton, M.A.

Or maybe she's just looking to keep her options open. After all this is an ex she's clearly had issues with him before. If it doesn't work out she can always fall back on you.

There are many explanations.

Most of them mean you need to walk with extreme care.

[Trippin2.0]

Firstly, I don't think its helpful to diagnose random people on the internet. We know nothing about this woman except she doesn't know which man she wants right now, and when based on that fact alone nothing in the OP even suggests BPD. Anyone can become confused under these circumstances.

Secondly to Gavin, I'm not quite sure what type of help and support you need right now, so I hope I'm not putting my foot in my mouth.

I'm sorry she did a complete 180 on you, maybe its not that you were the rebound, but more along the lines of she never found closure with her previous partner.

You said he cheated, and she fled, no contact.

So if he's coming into the picture out of the blue with some explanations or whatever, it could've definitly stirred up some unresolved emotions and "what ifs" for her.
Especially if she now somehow believes he never did cheat on her back then...

Idk what those 2 are discussing, I can only speculate about why she's so unsure and distressed right now.

Thing is, even though I understand not wanting to have any regrets (I also took back an ex - BIG mistake, but luckily I never dumped anyone for him) you just can't have 2 The One's, and the fact that she's that unsure, (or that the "competition" is so tight) makes me think you need to keep a safe distance from her.

She clearly doesn't know what she wants, and it seems like she expects you to "wait and see" while she figures it out ... You deserve so much better.

Sometimes people need to lose something in order to recognize its value.

I'm so sorry this has happened to you

[TrueMe]

I agree with Trippin2.0, Typically when your partner does a 180, another person is involved. It can really mess with a persons heart and emotions and it seems that that's what happened to your girlfriend. Obviously her ex has a big hold on her heart, and the reasons are probably very complicated. The last thing you want to be is someone's back up plan. Like what was already said, sometimes we have to lose something valuable to learn to recognize value when it comes along again. My boyfriends ex did the same thing. She ended it with him after a year together because a former love came back around and she wanted to give it a shot. My bf was heart broken, so much so that he moved 2000 miles away. Eventually we met and fell deeply in love, emphasis on WE. Then his ex contacted him, wanting him to come back, saying she now sees what she had in him, that she missed him. It messed with his head a little, but what we have was bigger and he was smart enough to see if he went back, it would only be a matter of time before she did it again. She still tries every 6 months or so to talk to him, though I think she's running out of reasons to call. Your ex is your ex for a reason. You deserve someone who is complete enough to love you fully.

Originally Posted by Trippin2.0

Firstly, I don't think its helpful to diagnose random people on the internet. We know nothing about this woman except she doesn't know which man she wants right now, and when based on that fact alone nothing in the OP even suggests BPD. Anyone can become confused under these circumstances.

Not how I meant for my post to be interpreted but I can understand how it happened. My apologies for not being clearer.

I meant to give other explanations (including that stereotype) and then point out that there were many reasons that she could be doing what she was doing and that the OP needs to be careful thinking too much about this.