First off, other peoples' rude actions and opinions are most certainly
not your fault! That's on them, not you. It's your body, and you are at liberty to do what you want with it! It's really none of their business at all. Wow, seriously. I can't get over what jerks those guys are.
Secondly, and I know this is tough, but try not to compare yourself to other people. This is one that I had to learn the hard way, and am still learning. When you're comparing yourself to others, you're comparing your worst to their best. You never see the things that they're insecure about or bad at, and trust me, they have those things. It is
not your fault that your genetic makeup means that you lose weight slower than your friends.
Please don't do anything rash. Always remember that losing you would traumatize your son far more than some random jerk's laughter ever will. He needs you, and he doesn't care how much you weigh. You're his mommy.
Depression isn't something you can just shake off, and it always makes things like this feel much worse. I struggle with anxiety, and it likes to take every little tiny thing that stresses me out, even if it's not a problem at all, and turn it into an insurmountable mountain of stress. This is tough, but you have us in your corner whenever you need to talk things out. Good luck finding a support system in your new city. If things are getting that bad, see if you can't find a counselor to talk things through with. It really is immensely helpful.
Good luck, and don't let the dregs of society get you down!