I think that you may be going too fast. I understand how you can fall for someone you've met online and talk to on the phone. Yeah, I've done it a few times before, so I'm totally not judging you. These things sort of happen.

What I am concerned about is the fact that this guy seems to be trying to control you when he gets mad that you don't text back within a certain amount of time. I think this could just be the beginning of what you see in terms of how controlling he is.

I recall a story of a person who moved to another country to be with a guy she met online. The guy was mr wonderful online/on the phone. It wasn't until she moved in with him that she discovered how nasty and abusive of a person he was. Unfortunately this story isn't all that uncommon in that people can/do show one side of themselves over the phone and online, but in person it is a very different story. In many cases its not done with malicious intent, rather its just a function of not being able to fully see the person until you know them in person.

I strongly urge you to step back from this relationship. Please don't bow down to his demands that you respond to texts immediately. If anything, I'd stop responding. He doesn't own you. And really, when it comes right down to it, he doesn't trust you. If he needs to keep tabs on you 24/7, it means that he doesn't trust you when you're "away" from him so to speak. Could you honestly live the rest of your life always having your phone on you and having to respond to texts within 10 minutes? (or however long.)

As for this relationship up/down being a part of BPD? I don't think so. Its pretty common for relationships, especially those of the online variety, to be hot/fast at first and then fizzle out. It can be exhilarating to meet someone online and have SOOO much in common with them that you two are pouring your hearts out to one another before you know it.....but when you're only talking/texting, there's only so far that the relationship can progress.

I think that you're seeing red flags now. Please don't ignore these red flags. The right guy for you is going to trust you and not demand that you text him back within so many minutes. You are a free and independent person, and shouldn't have to bow down to his insecurities. The right guy is going to trust you and understand that you will respond to his texts on YOUR time. After all, texting is not urgent, and IMHO its ok to not respond right away unless you're in the middle of a back/forth text conversation and then its just sort of rude (as you would never walk away from any other conversation in the middle, the same applying to text conversations). And if it is a matter of you not responding to him in the middle of a conversation, then give him a "GTG TTYL" so that he isn't sitting there waiting for a response. (I have this problem with some friends who don't understand that just because its texting doesn't mean that its not a conversation if we are indeed having an immediate back/forth interaction.)