They're most likely just messing around.
My buddies always do this sh1t. Even when I was in highschool. And like Norwegian said. What I do I escalate it until they give up and them I call them a fag and continue what I was doing. If they're not gay it should work. If they are...sorry. One of my friends in HS would get really pissed when anyone messed with him like that. Then we found out hes gay, still one of my good friends though (but I digress). If your not comfortable with it then make sure to set your boundaries with them, and deal consequence to whoever crosses the line.