So upset right now...

I'm really upset right now. My boyfriend and i have been together for more then a year. I really love him and we've been very Happy, especally this past month. My friend has asked me to check out some guys on a dating site with her, and i did, when i came across the biggest shock, I saw my boyfriend on there... I'm completely shocked, I don't know what to do or what to think... I feel like I don't know him. Why is he spending time with me if doesn't care? What is he doing?