I did the same thing when I lost my virginity. It felt like a waste and it was very painful afterwards, especially seeing him at parties and he would act like nothing happened, it hurts to be disregarded as a mere "fuck" or "hook-up". I was so ashamed of myself after that; I felt soiled and dirty.

In time you will come to terms with it, probably when you have had time to really learn about the experience and how you really feel on the subject of sex. After a while it won't matter anymore, it becomes just another thing that happened in the past. Hopefully in the future you will know what is best for you and your body. We are young and will do many things that we aren't ready for and might regret later but hopefully we learn from it. So, that is all I can really tell you is learn from it and that a lot of women and girls know how you feel.