What Causes Vaginal Discharge And Burning Sensation After Sex?

Hello, I am having a problem. I am having a discharge that is clear but then later in the day dries up yellow and is hard with a mild smell, what could be causing that? Also I tend to have a burning sensation (which kind of feels good/bad) after unprotected sex or after he pulls out for a second for about 10 then it goes away, is that? Also my boyfriend couldn't get the smell of my vagina off of his hands for a while. I went and got tested and all my results were negative. Why is all of this happening to me?