My 10 year old son will not participate in anything our family likes to do. Any suggestions?

It seems like no matter what we do he doesn't want to be involved. We'll pick what we think is a fun activity and then he will spend the whole time disengaged, reluctant, and beligerent. He's no fun to be around and yet I feel like he's being isolated if we leave him behind and carry on without him. I feel like if I allow him to constantly be the one who dictates what we get to do then he's controlling the family however, if I try to force him to join in he ends up getting a headache or other ailment that ends all the fun. We're all getting really tired of his bad attitude and I just don't know what to do anymore. Please advise this frustrated mom.