Why do my friends never invite me to anything?

I feel like my friends are avoiding me. I hear about everyone going out to parties and hanging out, but i feel left out. I really dont have any odd quirks to me, and i guess people think im funny because i was voted one of the funniest 3 people in my school yearbook. I do my best to be nice but it seems like nobody ever calls me to hang out. I always have to be the one th invite them and it feels crappy. It feels like my friends are avoiding me and making aweful excuses so they dont have to be near me. Its really making me depressed and i feel down all the time. Any help would be great, thanks.