Is it a problem not to sweat even when there a lot of heat, or when exercising? ps: i feel extremely hot inside, but sweat just doesn't come out!

Can be a problem: Sweating is the way in which your body cools itself off, and so not sweating, particularly when exposed to high heat or when exercising can be very problematic, as your body's core temperature may rise to an unhealthy level. Not sweating can be a result of dehydration, so you may want to monitor and increase your water intake. Also talk to your doctor to rule out a medical cause.