Why is there blood in my urine?

A month ago I was diagnosed with bladder infection because there was a little bit of blood in my urine after I urinated. I was given antibiotics for it, and after I finished my prescription, it went away.

Now after this, I ejaculated, and I found blood in my semen this time. I went back to my doctor. He said that it may be a polyp growth, so he gave me more antibiotics. But when I took the first pill, I got a fever and was unable to take the rest. After that, I got an ultra sound test. The results were negative.

Today, I urinated and I had blood in my urine. But that was only after I forced myself to urinate, like how after you do urinate, but there is still a little bit left of urine, and you force it to come out. That's when the bleeding occurred. It doesn't hurt or anything, it's just blood. I did some research and I read that it could be a broken blood vessel, or it could be prostate infection.

Could you give me some opinions on what this might be? My doctor said that if the first ultra sound test doesn't work, I'd have to get another one. Now if THAT doesn't work, I'll have to go to a specialist so that they could stick a camera in my penis to see the problem.