Is it okay to feel this way? What should I do?

Okay, so my boyfriend and I have been dating for almost 3 years, and he is so amazing! He just graduted from highschool and I have one more year to go before I do. Anyways, we went to a grad party for one of his friends that goes to a different highschool, along with some more friends, my bf has known them all since middle school. Their pretty cool and I've grown to know them well. Last summer I met one of his friends at our usual parties, I didnt think much of him at first, but through out the summer, Id see him at all the group hangouts and he was always nice and really funny, and we had some things in common, and out of all my bf's friends, he was the one I got along with the most and he actually pays attention to me. So by the end of the summer, I realized that I sort of liked him, and I always got excited when ever he talked to me. Then I wouldnt see him for like 4 months and Id get over the feeling and focus on my boyfriend, who two years ago, went through the same thing Im going through and cheated on me, I forgave him and we are past it now and really close, but then this summer rolled around, and I saw him again, and now I cant get him off my mind. Things are running dry with my boyfriend, Im never interested in kissing or anything sexual, and i feel like an asshole because Ive liked his friend for almost a year. If I broke up with him, I dont know what would happen, things would be so differnt, and Im not sure if this other guy likes me because I dont see him or talked to him, and I keep wondering if he feels the same way. Everyone thinks my bf and i are ment to be and are gonna get married, and Im too busy thinking about his friend! Im so confused, I feel like horrible! Is there something wrong with me? Is it normal or even okay to feel this way about him while im in a serious relationship? Am i a terrible person? I need some advice...what can i do?