what's going on?

I am very careful about unprotected sex. We don't do that around my fertile window and any other time, he pulls out. But we mainly use condoms and pull out method. Recently, I've had a slight UTI for about 2 or 3 weeks now. And I'm 5 days late on my period, which isn't typical. So I took a test today and it was negative but I still don't have a period or any symptoms of it. Just a slight headache. What's going on? Can a UTI mess up my cycle? Or am I possibly not pregnant or is it just too soon to get an accurate test?