I've had vigorous sex with my girlfriend and when I stopped I noticed that a little blood was coming from my penis. I don't know what caused this. The other day when I tried to engage in sexual activity my penis felt really sore. I've been frequently urinating and it hurts when I have an erection. I also smoke weed as well so I'm not sure if this could also be apart of the problem. I'm really concerned and I plan on seeing a urologist but I would like to know what's going on so that I can calm down a little.