I exercise regularly. After running today, I got clear, fluid filled bumps all over my stomach, chest, under arm, and back. They don't hurt or itch. I could wipe them away, but they would pop back. They only went mostly away after a long, cool shower. I did a regular run and didn't get overheated. I also hydrate before, during and after as usual and wore my usual, clean running clothes. What are they and should I be worried?