Am I a horrible girlfriend?

Okay, so me and my boyfriend have been together for almost two years...well dating for two years...its been four years since I first kissed him. I was convinced that I was completely in love with him. Now I'm not so sure. It's been so long since I'v e been with someone else. Honestly, he was my first everything...first kiss, first boyfriend, first lover, etc. he hasnt been my only kiss or boyfriend..we'v hit bumps along the road, but now that he thinks everythings fine, im not. Im bored. I dont know what to do. I do care about him, so much and I dont want to lose him, but Im bored with him. I havent felt a spark in so long. I dont know if this is normal, and if it is, this sucks. I dont want to be bored with him. I want everything to be the way it use to be. And ive caught myself flirting with another guy. Someone in my forensic class. Hes so sweet to me and he brought the butterflies back. Butterflys and fireworks I havent felt in a really long time. Ive never kissed him or anything but, I still get these feelings I shouldnt be having. I dont know what to do? Am I a horrible girlfriend?