UTI issue

So I read somewhere that by taking antibiotics, it makes the pill work less. It's been only a day since I started taking antibiotics for my UTI but I got my period or I'm spotting a lot and now I have to wear a pad. I want to still be able to have sex. Opinions? I was supposed to take the antibiotic for 5 days but I heard it goes away on its own. What should I do? Should I continue taking the medication or stop