What should I do about this situation at work?

This may seem like a very peculiar question, but it has been eating at me for several weeks now, and I have to get advice from somebody, because its keeping me up at night. Anyhow, I have a staring problem. I often find myself gazing at others; sometimes without even realizing I’m doing it. I pretty much stare at everyone, and it has nearly gotten me in trouble several times. I was staring at a male cashier at work one day in the supermarket where I work(for what reason I don’t know), and it was beginning to aggravate him. Being the humble personI am, I apologized to him in the breakroom one day several weeks later. I said something strange like: “I was staring at you the wrong way one day a few weeks ago, and I just wanted to apologize”. “Sometimes the heat outside makes me act funny, and do strange things” He just looked at me, and said: “I don’t remember that”. Then I said: “Oh well, just forget I said anything”. Then he just snickered and started giving me an odd look. The thing is that I’m a bagger, and I do spend a lot of time in the hot sun, and it DOES make me act weird. It could be a medical condition–I don’t know. Anyhow, whenever I try to pack groceries on his register, he tells me that someone is already bagging there. Or he comes up with some other excuse. I really don’t want to assist him, but sometimes there’s nowhere else to bag, and I end up on his register. And I certainly can’t just stand around all day. This guy is much younger than I am, and I’m pretty sure he must think I’m gay. But I’m not, and I never have been. Anyhow, I don’t know how to deal with this situation anymore. The guy is probably gossiping about my odd behavior all over the store. I can’t even enter the same room with him, without him giving me dirty looks. I don’t want people to think I’m gay or crazy or anything else that’s going to ruin my reputation. What should I do?