My boyfriend and I have been doing sexual stuff for a while now. A month or two ago he complained of having bad stomach cramps and some blood in his...well, to put it delicately, excrement. Now I'm getting the same thing. Also, I've noticed in the past couple weeks I've had increased vaginal discharge (clear, almost watery). I'm just a little concerned - could these be symptoms of an STD? I've been faithful and I trust him completely, I'm sure he's faithful too...what STDs can be transmitted through monogamous sex?