How do I get these guys at work to stop bugging me?

These guys seriously can't take a hint. I shove the fact that I have a boyfriend down their throats and always ignore their texts (yeah they found my cell number at work). I am sick of being asked if I want to go out for drinks with men twice my age. They keep asking why i never answer and i say i was busy, cant they take a hint? How do I stop this? I've already spoken to a supervisor but he says oh their harmless don't worry. Ugh this is the problem with working in a mainly male environment and being the only female. And I am pretty overweight (190LBS) so I'm confused as to why everyone hits on me like I'm freaking Megan Fox! I would be cool with just being co-workers with everyone there, I go to work to make money, not find a 50 year old man to date! Someone please I need advise, what can I tell these guys (aside from making sure they know I'm taken and not interested in drinks) to make them knock this stuff off? Have you ever been in a similar situation? Help!