UTI / should i take the medicine

Okay so i had sex this weekend. I was fine but then we used lube & my vagina started burning. & today my vagina has kind of like a burning feeling, even though we didn't use that lube today. Well anyways, I've had a uti before and I'm pretty sure that was from forgetting to use the bathroom after sex. & thinking back i might have forgot to use the bathroom this weekend. Now when i wipe there is just little drops of blood. I feel like i have to pee all the time. & last time i had a uti i thought it took me a couple days to notice. & now I'm wondering if I'm realizing right away before it starts getting the really bad pain that follows? I have medication for a uti, I'm wondering if i should take it just incase