Recently I have had burning sensations while urinating after (but not directly after) masturbation. It will last up to 18 hours after the previous masturbation session. However, if I drink lots of water (like 4 16.9 oz bottles it doesn't burn as much when I go. Also, after the masturbation session and ejaculation, it feels like there is something stuck inside my urethra (like un-blown semen) and every time I muscularly constrict my urethra it feels like there is something trying to reach the top but it never does. I have been tested for stds, uti and kidney stones but all have come up negative.