I Had Sex A Week Ago, Unprotected And I Was

i had sex a week ago, unprotected and i was on my period- a few days later i notice that it hurts when i urinate, like when its about to be done it starts to hurt. i assume its a urinary tract infection because ive been driving around a lot and ive been having to hold it in, bad idea i know.
lately, ive been scared that its actually an std and i have a fear of going the doctors. since the pain started, ive been drinking cranberry juice, water and taking vitamin c pills, it used to smell when i peed but not anymore, and it feels a lot better than it did- but its still there.
last night i woke up with a pain in my back, below the ribs, which made it extremely hard to fall
back asleep. whenver i would lay down not on that side the pain still spread bcus small amounts of pressure were still being pushed onto my lower left back. i woke up later and it felt a bit better, but as the day went on today it (my back) started to hurt when i walked and urinating didnt feel as bad as it did the day before, but my back was killing me.
i decided to masturbate to see what would happen (clitorally) and afterwards both sides of my back started to hurt like the one side did last night, below my ribs
and my lower abdomen/stomach maybe is hurting the same way as well and i cant do anything without the pain
its makin me feel nauseas,
i went to the bathroom after, peed, it was painful (but only at the end) wiped, there was yellow with a small string of blood in it
i look in the bowl, its clear so i assume its coming from
somewhere else

the blood part makes sense because i just got off my month long period (due to starting the pill) a few
days ago, and i did have sex again yesterday but it doesnt explain the pain im having

im really scared and i just need to know whats happening, did i sleep
wrong? is it a uti? an std? all
of that? i dont know