Ugh boy problems

Ever since middle school me and these 4 other people (3 girls 1 guy) are close we go to the same school and so we hang out before school and eat lunch together. Beginning of 10th grade year the other girls in the group made a bet that me and the boy would date before 12th grade and it didn’t seem like much because we didn’t like each other but as the year went on we got closer I guess you could say. And then I found out he liked me from one of my friends and I didn’t know how to feel. A part of me was excited kinda that someone actually liked me but then another part of me was mad because I didn’t want the “bet” to be true so I sorta distanced myself because truthfully I liked him too but I didn’t tell anyone. Recently he finally had the balls to tell me and because my ego is so big I just said okay. And I’m really starting to regret it because now he hangs out with other girl and it just makes me sad.