So long story short, me and my high school sweet heart have been dating for over 3 years and we went to different colleges. She stayed right at home and commuted but I went to a school 2 and a half hours away. And this move was very hard for the both of us because in high school we were always with each other and always doing something. She did not do so well at first and I was somewhat okay because sports kept me from thinking too much about it. But then I got injured and started to really think about it and it got worse before I even knew it. While I was away she has been having trouble and stress from work, school, family issues, car problems, and found out her mother has breast cancer. And she would normally come to me and cry on my shoulder or cuddle with me till she felt better and we would just talk it out, so I would help her anyway i could. But I feel these things have been such a burden on her that she didn't know what to do without me and she became more independent, and she started going to the gym and making new friends to make up for it which I thought was great. But now, school has not been working out for me, so I'm decided to move back and attend the same school as my girlfriend hoping that things would restore and she would be happy again.
But overtime she has kinda changed when she became independent. For example, she brought up a lot of problems that we have had in the past and said that we would need to fix them (and it was kind of out of the blue) and I have been dedicated to fix these problems and she can see come progress but she's not sure, even when I'm giving it my all. And she wanted to talk more about out problems in person, so I would visit home, but she wouldn't really talk to me, I felt I was almost talking to myself, and anything I said she would just yell at me and tell me something bad about it, would change the subject to worse, and would just say she doesn't know. She said that she is a little stressed from me moving back because she has been on her own for like 3 months and now doesn't know what she'll do when I go back.  Like I would visit and we would go on dates and they would be fun and she would have a great time, but over time it's just like something is bringing her down and she doesn't know what to do, and she doesn't know how I can help, even if I can. We both really want this relationship to work because we believe we were meant for each other, just don't exactly know what to do in this rough patch. This is really our first problem that we've really had and both don't know what to do. Some advice would really help, especially on a girl's point of view on why my girlfriend might feel this way.