How do I control my jealousy? It gets so bad that if my friend/significant other is even just laughing with someone else I get extremely jealous and feel like I'm not good enough.

I think it's great that you recognized your feelings of jealousy. Many people experience jealousy, myself included. Your friends are your friends for a reason. If they didn't think you were good enough, you wouldn't be friends or in a relationship with them. When I experienced these feelings I remembered this, and it immediately helped me. In these situations I also tried keeping myself busy and made sure to communicate with the friends I was feeling these emotions towards. I also made sure that I trusted them. Most importantly I made sure that I was confident in myself, and worked on my self-esteem, which helped me a lot. I hope this works for you!