Hey everyone. This is my first time on this forum, nice to meet you all. I want to ask about a psychological problem that caused my relationship ended. This could be kind of long, but that is how much it bothers me so I would really appreciate it if you guys can give me some opinions.

Just want to throw that out there, that personally, I am already someone with a mood swing who gets sad suddenly. Not sure if that is depression or it is just me.

The problem is this:
I had an argument with girlfriend over text back in middle of November of 2016 over something quite trivial but I have been having stress and depression problems that she may not know of. I never said anything about breakup or even hint it. I ignored her a few days, she sent a message asking do I want to talk to her talk face to face, all I said was "I dont know what to say, please give me some space, I want some time alone". She then want to confirm that if I meant want some time or wanting to break up with her. She then apologized and know it was her fault, but I didn't have the mood to reply. I have checked up on her social media from time to time during my alone time because I care about her, she did make some posts her thoughts about sad she was from time to time and she went out with her friends to have fun because I know she just want to occupy her pain. I feel bad she is sad too but I just didn't say anything to her. Then until this month, 6 months after our argument, I have learned she has gotten a new boyfriend, and I feel like ****, because all I wanted is just be alone for a while, not a breakup.

She is my first and only girlfriend, because I dont find girls just because I am lonely or for the hell of it. I love her and all but she did mentioned about wanting to get married and have kids before 30(she was 26 when we argued). This gives me stress more or less, but I never thought about backing out because I want to marry her, but I feel like there is a time constraint. Me being just graduated from college, working on my low pay entry level office job, on top of that, I couldn't even take care of myself yet, the idea of expensive ring, wedding, houses and kids is overwhelming. This gives me constant worries, what if I am powerless to fulfill those promises? what if I am wasting her time and youth?

Therefore, I work really hard, working 6 days, sometimes even 7 days a week with part time job on weekend waiting tables, try to save as much as I can to buy a house, or whatever expense I need for our future, as well as paying back college debt. Working so much also makes me feel exhausted.

I am the type of person that think I have responsibilities for all my girlfriend's problems and our future because as her boyfriend and as a man, it is what I should do to give her happiness, and this is just the way my mind works. But when I think I can't do it, I will have self blame, and thinking that I am useless, stress, and unhappy. This self-blame characteristic really took its toll on my mood and mental health on top of my tendency to suddenly feel sad. Besides the marriage stress, and the "if I can fulfill her goal" stress, I have other stress that I can't help to give myself.
For example, one time she has to go to New York City with a female friend of her to attend a nursing lesson. I have to work so can't go with her but I was really worried about her going to such a complicated place, even a female friend with her wont do much. That time I will have a feeling that I am useless and can't protect her.


So all these kind of self-blames, that makes me stress out and tired, caused me to want to isolate from her, but I really didn't mean to break up with her.

What do you guys think I can do now? Do you think she will think the same thing as my sister? Is it possible that I can get back to her if she know my perspective? I feel she really loved me but moved on, thinking I dont love her so I ignored her but that is not true. I really just dont know what to say and just wanted to be alone, that's all. I feel everything is too late now. Is what I did the wrong way to put my alone time in practice? I told her I want sometime alone, and in I just want to be alone, not like I want to be single. This really gives me a lot of regrets.