Penis “Blockage” problem?

Patient: Doctor(s), I seem to have a problem with my penis as of recent, I have no problem having an erection, but as of recent it feels like the pipeline is blocked in my penis, I was having sex with my girlfriend, and I got off just fine, after that, it felt like some of the sperm was stuck inside a little bit, and wouldn’t come out.. I attempted to pee later, and it still felt like something was blocking the path a little, yet I had a solid stream of urine with no discoloration, the next day, I tried to get an erection, and I did, but when my blood vessels in my penis expanded all the way, the head of my penis hurt a little, but after a little bit of sex the pain went away, but when I was close to getting off, I couldn’t get off, it felt once again like something was in the way, then my penis softened up, and I was unable to get off. I was wondering if you knew what this blockage feeling is? and how to cure it? I’ve been tested for STDs and am perfectly clean, my girlfriend as well, we’ve been together for quite some time now, and I don’t suspect any funny business on her end.