Hey Gawain, here's a suggestion. If you think others are laughing at you, you can ask what's funny? This happened to me on Thanksgiving, I was with my family, I said something, and everybody else laughed. I asked why everyone was laughing at me. As I remember, nobody answered, I let it drop, and we went on having a good time.
I'm sure you had a painful experience of being laughed at, earlier in your life, when you really were being excluded and picked on. But you don't have to react to this the same way as you did when younger. You can ignore the laughing, join in the laughing, or ask what the joke is so you can enjoy it too.
With this thought in mind, you might try going back to that group and express what happened to you the first time. I bet that people will respond quite differently than you are expecting them to.
_________________
A finger in every pie.