Not sure if this is the best place to post my question or not but here it goes.

I feel like I have a lot of trouble making eye contact with girls I see on campus. Whenever I get a look or at least I think I am getting one, I just have disbelief that they were actually looking at me or checking me out. If she is really cute I seem to lose all my confidence and think that no way would a girl that attractive be looking at me. I may catch a look from her multiple times, but I just don't believe she was looking at me. I just assume that it was because I looked at her first or some other reason. I know this seems weird but for some reason I just cannot get passed this.

For example this happened with one girl I see a few times a week on campus. Basically all the stuff I mentioned just happened. The first time I think she was looking at me was when I was walking away, turned around for a second and saw her looking in my direction, I was just kind of like, was she just checking me out? I just walked away and thought no way. It wasn't until a couple weeks later that I actually kind of believed it. I had walked past her with my back facing her to grab something (i didn't see her), when I turned around we made direct eye contact for a few seconds until she looked away. At that point I kind of believe it, but ever since than I continue to disbelieve.

I don't know why I am like this. I don't have much confidence or experience with girls (zero actually), so I guess that is a part of the problem, i just understand why I won't believe it. Any advice, or links to help me out would be really useful to me right now.

edit: Thanks for all of the responses, I didn't expect to get so many. Honestly all of the posts were very helpful. I'm going to use this advice to improve myself. It may take time but I hope I get there. Thanks all.