An Infection Getting Worse and Worse: Can I Just Wait it Out?

I am 15 and I just had sex for the first time last Friday. It was unprotected but he did not cum. The next morning I had pain. The pain continued through Saturday and Sunday. I thought the pain was from having sex for the first time, but it's now Monday and I realized stinging while I pee, cloudy with some blood in it too, in addition to constantly having to pee and never feeling empty. I have had chills, too. I am almost 100% positive I have a UTI, but there is no way I'm telling my mom and getting medical attention for it, she can't know I had sex. I've read into it in depth, and the more I read the more scared I get. I'm on a vitamin regimen and I am able to get a z-pack, which treats bacterial infections but I'm unsure if it'll help me. Will it? are there anything I can do besides drink water and wait it out? How long will it last untreated? HELP!