Burns to urinate after sex?

Emily • 20, midwest.
Every time my boyfriend and I have sex, I go straight to the bathroom afterwards to prevent a UTI. Lately, when I urinate, it burns that entire day and I have UTI symptoms (frequent going and burns) but the next day, they're gone. We've been together for 2 years and I know neither of us have STD's but I just want to know if it's normal or what I should do.
Also, I have gone to the doctor and tested for a UTI and I don't have one so it's not being masked or anything.