Whenever I get into various situations my face goes bright red and I start sweating a bit, why is this?

Its very strange as I can be at a party or with a group of people talking normally but when I get asked a question in class or if I walk into a library etc. My face gets very red. Its really annoying as it cant stop my ability of talking to people as I turn self conscious, however something Ive started to do is take it on and maintain confidence even if I feel almost embarresed for going red. Is it due to stress, nerves or just confidence?