I suffer from severe public speaking anxiety too. It used to be so bad that I would literally shake when i'm in front of everyone, so I can relate to how you feel. You are very brave for having spoken in front of a group of people at all. I know that it can be hurtful and hard when people make fun of you, but don't let them get to you. There are some things I do that helps me loads with reducing my anxiety when speaking in front of a big group. I always rehearse my text the night before, make notes in small cards to help if I freeze, and I also constantly remind myself to speak loud and clear a few minutes before I start speaking. I know it can be superficial, but faking confidence is key to actual confidence. If you are scared try making eye contact with 2 or 3 people spread evenlyin the crowd and continue talking to only this people.
You have nothing to be embarrassed about, know that you are not alone. :) Stay strong!