Urinary Tract Infection and Pimple-like on Vagina

I think I may have Urinary Tract Infection as i've been urging to use the restroom without little or nothing coming out. And throughout the day I have that urge to use the bathroom. I use the bathroom almost every hour and it gets really bad at night to the point where I can't figure out if I really have to pee or not. And most nights I have to wake up in the middle of the night. I highly doubt i'm pregnant. As to this has been going on for a month in a half. Now i've just realized I have this pimple-like thing on the left side of my vagina which comes and goes. And for some reason every time i've had it was when I was suppose to have my period, but didn't get my period. I'm now 4 days late on my period. This has happened before without the UTI. My question is...what is that pimple-like thing and could that really cause my period to be late? I know I said it happened before but i'd like to get my hands on some information before I see the doctor this week.