I have a karate class 3 times a week. Once in a church hall, once in a school hall and once in a proper fitness studio in a gym. For some reason, I have become ill the past few times I have trained in the fitness studio. About 10/15 minutes into the class I start feeling clammy, sick and light headed and have to sit out before I literally collapse. I have no idea why because at the other two places (church and school) I'm fine. Only difference between the places is that the gym has air conditioning and the other places don't. What could be causing this? Everyone else in the class is fine, its just me. I don't want my sensei to think I'm doing it on purpose to skip line-work as it always seems to happen at the same time, then 10 minutes later after sitting down I feel fine again for the rest of the class. I have a grading in two weeks and this is really bothering me. Thanks in advance.