What Causes Constant Vaginal Itching?

Hi I have been having problems for about, 3-4 weeks now, I became sexually active just three months ago. And around 3-4 weeks ago I noticed that my vagina was burning when I weed and itching and just felt very uncomfortable. I left it but it felt uncomfortable to have sex, and my discharge smelled fishy. I left it longer thinking that It would sort itself out. Then I came on my period 1 week early! And it was extremely heavy considering im only 16 and i weigh just 5 1/2 stone. It didnt even stop in the bath. The other symptoms settled down a little, but it still burned a bit when i weed: then my period stopped for a day. I thought it was over but clearly not cos a day later it started again, but lightly, like, spotting. It was a dark brownish colour. My period stopped after 7 days, (two days ago) and i thought the problem down there had gotten better. But last night I had sex with my partner and afterwards my vulva swelled up kind of like orange segments, but very very big on both sides. It burned for me to wee after sex when my vagina liips were like it. Iv had a bath and put cold stuff on it but my vulva has stayed swollen all of today and is a different colour. Whats wrong with me?