I'm a 28 year old man. I had fever for about 2 days,the fever stopped but after that I started to have brown-dark urine with some kind of mucus coming out with it for about 2 days,after that it cleared up to normal, but now is my semen coming out brwon-dark for the second day.. no other symptoms.. I'm sexualy active and I exercised hard one day before it happened, I don't know if this is serious or not?

It sounds like blood to me.

I would definitely take this seriously. You really do need to go see your doctor about this.