I feel so left out all of the time, what should I do!?

I have a few friends but most of them have tons a friends, I'm trying not to be as shy as I used to be but its not working. Its the last year of primary school and everyone in my grade is friends with eachother- except for me! I try to be funny around them and add my own comments, but they just don't seem to like me. It really takes my self confidence away and its makes me feel alone and sad. Most of the time when my friends are having fun- I'm always the one left out of things!! Help please what should I do?