Relationship Help please?

Okay my girlfriend and I have been dating for quite a while now. It will be 3 years come june. We met in high school and have made so many memories. The beginning of our relationship was great and dont get me wrong we have definitely had our ups and downs. In the beginning of the relationship she wrote me a heartfelt note saying how i changed her life so much and that she doesnt know what she would have done without me. Sometimes she does have issues within her family and im the first person she comes to and ive always been there for her because i love her so much. Things have changed a little since then though. She moved away to another college and im commuting to a local school. Her school is only an hour away tops and im willing to drive down there whenever i have a chance. But a few months ago when she started college she called me and told me that we needed a break so thats what we did.I of course was hurt because we had told each other multiple times that things wouldnt change when she went to college and im working towards possibly transferring out there so i can be closer to her. During our month and a half break there is another guy who entered the picture and they were getting closer and closer and i think they maybe dated for a short while. After a few weeks of them dating she called it off with him because she missed me and wanted to work things out. we talked about it and we decided we would give it another shot. We know there are some things that we need to change whether it be my habits or me being more driven becuase sometimes i can get lazy and nonchalant about things. However, her and this other guy are still very close friends and he still likes her. The other weekend I went out to visit her at school and we got into a fight. She didnt like that i had hung out with a few girls (who were just friends) and my friends the day before. i just told her that i needed her to trust me because thats the only way it was going to work. ive had to trust and accept this other guy so why couldnt she trust me. in the heat of the argument she said that sometimes she thinks that the other guy is better for her than i am because he made her a better person. i was extremely hurt and i just decided to head home because i didnt want to fight. I hate fighting with her. She came home for the weekend and we went on a date. The date was alright but it was kind of awkward because we didnt really talk about what happened the other day. She asked me what was bothering me and i told her if she really meant what she said the other day (that the other guy was better for her) and she said sometimes she does feel that way but not all the time. But she told me she had a little bit of feelings for the other guy and she also had feelings for me too but she was losing them because i havent shown her the change she has been asking for. i am trying to better myself for her because i know i can become a better person. i just need to apply myself in more things. im just so confused as to what to do now. I know we lost the spark that we used to have but i want that so badly. How can i show her that im serious about changing or that i love her? i just want each of us to have the mutual feelings we used to have for each other back. i dont want to lose her. She made me a better person. But i dont know what to do regarding the other guy or our relationship. i want it to work so badly i just hope it isnt a lost cause...


Thank you for reading this i know i typed a lot. Any help or clarification would be greatly appreciated.
Sorry about the formatting problems guys...im not too familiar with this site lol.

And she only wants me to change so that i can better myself. its not for her its for me. i just get lazy. She wants me to succeed and i want nothing less for her.