Sti/std

melissa
So let's say you have unprotected sex with multiple people (and I mean without a condom not without the use of birth control pills). If you don't have an std and none of the people you have unprotected sexual with have stds can you still get one? Where do they come from? I recently had a new partner and had no symptoms but got tested anyway and the results were negative. Then I slept with a really good friend that I know for a fact is clean and we are both experiencing some irritation. So now I'm worried I somehow gave him something even though nothing showed up on my screening.