Hi Sade, I'm Ceri aka. Stumpy...
You sound like my American equivalent, I too have had people stare at me, or grab my arms, or feel uncomfortable due to my mental illness, and like you too I'm fat, my boobs are huge, and I too hate being hot and sweaty. However I refuse to be bullied by others, and wear short-sleeved tops whenever and where ever I please.
For anyone that doesn't think this is okay, they are not important, and don't have the right to make that kind of decision, or to demand to know why I would harm myself. I actually had a complete stranger snatch my blade off me just over a week ago, it felt terrible, and I know he meant well, but it made me feel very uncomfortable with my own thoughts and feelings for just over a week now, until I met with my counsellor earlier today to discuss it. I usually try to keep my self harm private, and not harm in public, but I was very near crisis point when I did this.
You are not alone, you're doing the right thing, try to stay calm, wear whatever you're comfortable in, and try not to let others bother you, and the next time someone grabs you, my suggestion would be to simply say, "Excuse me! That's a private issue, do you mind not touching me?" this generally worked for me and eventually stopped it from happening. *hugs*