What's wrong with me down there? Uti? Pregnancy? Something else?

I'm a 20 years old female and I lost my virginity to my boyfriend of 6 months, on the 18th April. I'm on Cilest for birth control and he the last time he had sex before me, they used protection and he's been tested so he's clean.

Afterwards I itched a bit around my vagina but I could cope with and presumed it was due to the fact I hadn't had sex before so had been stretched, we continued to have sex for about 3 days while I stayed with him. The itching continued but it only became unbearable a few days after I'd come home. I thought it might be cos I had been really wet and was now dry (sounds silly I know) so I made sure I drank at least 10 glasses of water a day and stayed away from caffeine and used tea tree oil which all helped.

Then I got my period and I didn't itch at all, that finished last week and the itch came back afterwards but not too bad, then yesterday peeing burned and hurt and today it does a bit too and it's dark with wisps of 'bits' in (don't know how to explain it better sorry). I also feel really nauseous today.

Sorry for the detail, I am due to go the doctor at the end of the week but I'm not a fan of medicine so if anyone's experienced something similar and could pass on some advice or can prepare for what the doc will say please answer. No silly, immature answers though please. Thanks in advance