Learn English from funny kids

Basicallly I laughing is hard for me, I can find things really funny but I push out a little forced laugh. I wish i could just have the long, almost crying, belly laugh. The only times I do laugh are the most inappropriate times: church, plays (not funny parts), etc. I'm so jealous of the people who can just laugh so easily, I feel left out when everyone is laughing and I can't. Help me make my laughing abilities easier?
　　
　　Please don't say "Loosen up" or something because I can be with my closest friends/close sister and still have this problem.
　　
　　But my ha-ha instinct could be activated by the following videos only...