It may be a combination of things that have upset him he may feel that he has no one to rely on and was relying on you and now that someone complained he felt that it was best to just do it himself as far as something else being wrong, depending on whether he is a gay male or if he is in the closet. If he is an outwardly gay male then he may think that dating you will make people think that you are getting special treatment and aren't earning your keep around the store and alot of people think that workplace romances can cause a string of problems and if the other employees see you together and then complain that can get him in trouble. There are pros and cons to dating someone in the workplace. Looking at the contrast of meeting someone randomly at a bar to using the office as a dating pool. In the workplace, you have at least one thing in common already but also there may be a no dating policy, or they may not take well to dating within the office because of sexual harassment lawsuits.
Other potential problems enter when conflicts arises in the relationship and the couple can't work together. Thus, dating at work becomes messy. The conflicts may be a break up or a fight that is brought into the workplace or conflict within the workplace. Other conflicts may be caused by jealousy or rivalry from others working with you maybe the female thatcomplained about the scheduling you did. Maybe one person in the relationship is a superior in the workplace. This may cause tension amongst coworkers. People may question the effort and qualifications and may think you are getting by because you are seeing the boss. Of course again, there is always the issue of sexual harassment in such a situation as well which most companies would rather discourage.
No I think if you can talk to him then I would talk to him about what is possibly bothering him. I would also consider giving him some time, it take some time for him to get used to the fact that he is attracted to not only someone he works with but another man so I would wait it out a week and then make your decision then. If worse comes to worse I would suggest putting in a transfer if things get too bad.
I wouldn't make any hasty decision right now the worst thing to do is to make a snap judgment and then regret making it later, just give it some time and relax around him if he see that you are stressed it will stress him out also.