I ruined my relationship and I don't know what to do.

Okay, so I'm 18 years old, and I've never been in a serious relationship before. I don't really know why. I've had boys who have wanted to date me in the past, but I have just always been a very independent person. I started college this past fall, and I met a boy. We clicked immediately and we became very good friends. He had a girlfriend of almost two years at the time, and I didn't have an interest in dating him anyway. He was just a good friend. He was having a lot of issues with his girlfriend, and when he broke up with her, I was there to comfort him. We started talking a lot more and he started to develop feelings for me. After much playing-hard-to-get, I finally realized that I liked him too and decided that I really wanted to give this boy a chance. He was really sweet to me, and I ended up completely falling for him. We officially dated for a week, but at the end of that week he told me that he really cared about me, but didn't feel comfortable getting right into another relationship again after his last one ended so badly. This I completely understood. I really liked him, so I wanted him to be comfortable with everything, so we decided to take things slow. So we continued to spend a lot of time together. We pretty much acted like we were boyfriend/girlfriend. But after about 2 months of this, right before we left for winter break, I noticed that he was texting his ex-girlfriend. I was really bothered by this, but I was afraid to bring it up because I didn't want to seem obsessive. But because break was coming I decided it was important to bring up. So I just casually asked him why he was texting her and told him that it made me feel kind of insecure. He was extremely apologetic and said that he really liked me and shouldn't have been talking to her. I asked him is if still had feelings for her or if he had any interest in dating her again. And he looked straight into my eyes and promised me that he didn't. So I believed him. But about half-way through winter break he stopped texting me. I was the one who always had to start the conversation. I still trusted him so I tried to tell myself that it was nothing. The first day back this semester, he asked me to go for a walk with him. So of course I agreed and when I went to his dorm room , he had pictures of him and his girlfriend all over his room. I was obviously surprised and hurt, but I didn't know what to say. So we went on our walk and he acted like everything was the same. So I brought it up and asked him if he had gotten back with his ex over break and he said he had. I was so distraught. I didn't know what to say. I felt heartbroken, used, and betrayed. I liked this boy so much and had given so much of myself to him in such a short amount of time. The worst part is that I felt it was my fault. I felt that I just wasn't good enough for him. I just couldn't live up to his ex-girlfriend. I still liked this boy so much that when he asked if we could still be friends I said yes, even though I knew in my heart that friends would never be enough for me. I guess I was just afraid to lose him, so being friends was better than nothing. We talked a lot less after that. I tried to play it off like I was okay, but I was truly feeling lonely and depressed. After about two weeks of barely talking to eachother (and when we did talk it was very tense) I couldn't take it anymore, so I broke down and told him I missed him and wanted him back (pathetic I know). He then told me that he and his girlfriend broken up again, and that he also missed what we had before. He kept saying these sort of things to me, but he never actually said that he wanted to be with me, so I was very confused. And every time I tried to text him to ask him if we could talk about it, he would ignore me or say that he didn't want to talk about. This is where I know I messed up. I started to act clingy (I know this was worst thing I could do, but I really couldn't control myself). I continued to text him and kept telling him that I missed him. I continued to pour out all my emotions and feelings to him and he stopped responding to me. He won't even respond to simple texts anymore. I don't know what to do know. I like this person so much! I have never felt this way about someone else. Even though he lead me on and pretty much kicked me to the curb without a second thought and without talking to me about it, I still can't help but care about him. I don't know what it is, but I have such a strong feeling about him that I just can't let him go. I don't know what to do because I know that I ruined everything and I just want him back. Not even as a boyfriend, but as a friend. I can't live with myself feeling that he thinks I'm some clingy little girl. This person is very important to me and I need him in my life one way or another, and I don't know how to fix it. I know this is a long post, but I am in desperate need of advice. I just don't know what to do. Any advice would be appreciated! Thank you!