infection...

So I am 16 currently sexually active. Always use a condom and have only been with one partner. Who has no STDs. For about a little over a week my vagina has been sure itchy and right after I pee it feels like I still have some pee left, but none comes out. Also my pre has a very strong odor. I know it's not a yeast infection. I'm thinking its a UTI but I'm not forsure. Help please?