UTI help, kidney infection?!?!?!?!?

Okay, here is the deal. I was at work, about 6 days ago, and it was a fast progression of burning tingling feeling leading on to me not being able to leave the bathroom with out peeing all over my self. after i got home, i later found out through research on the computer that i had a uti. probably picked it up from the famous 7eleven bathroom i like to use when on break. i never went to the doctor for it. reason being is bc i dont have health insurance and went to a clinic and found out that i have to pay 250 just to be seen. then the cost of the test then the cost of the pills. i really dont have the money for that so i started taking azo and cranberry juice along with supplements, this helped quite a bit, but then it came back almost as strong as before. my gf friend had an old prescription that she had from her uti. she gave me it, i picked it up from walmart. its nitrofur mac 50mg mylan cap yellow 1650. i know its dumb to have taken her pills but i didnt want to cough up that kind of money. it was a full weeks worth of pills as well. ive been taking them for 2 and a half days now, this morning i felt pretty much alright. burning has resided, i can hold my urine just fine. but now.... my back is killing me! i really dont know what to do or what the problem is, kidney infection? i want to go to the hospital but its way to damn expensive, should i wait till morning and go pay the damn clinic or should i just go to the hospital now? i was told by friend you have to pay money up front, and told by some you dont. whats true and whats not...