Orgasmic sensation in vagina. Treat it?

Okay, so this started about a couple of weeks ago. I was sexually active earlier, but I haven't done anything in three months. I've been experiencing some weird, orgasmic sensations once I'm done peeing. I can also feel it throbbing. My bladder feels full, even when I'm done peeing and I've been urinating way more than the usual. It gets worse at night but persists even during the day. It's exhausting and there are times when I can't leave the toilet seat because I can feel my bladder is full but I can't pee, because I already have. Masturbation is a relief. But it gets back to normal as soon as i stop doing it. I could even pin point a spot in my vagina which could be generating these sensations. It is extremely uncomfortable. Is it an infection? Or what is the problem? How can I treat it? I have my exams in a couple of weeks and I can't afford to mess them up. Thanks.