If you've had it for four days, then you really have to go to the doctor. Honestly, if I have symptoms for more than four hours I go. It's been possible for me to drink water and cranberry juice when I have that first inkling that I might be getting one and then somehow stave it off and have no more symptoms, but once it hurts or the urgency starts, it's all over. It may go away for a few days -- even a week -- but then it comes back with a vengence, and I go to the doctor.
I just skip all that pain and go right away now. You can get put on a payment plan. There's no interest on hospital bills, so you can wait until you're better off, if money's your problem. You may even be able to find a clinic in your area that has a sliding scale. Just don't ignore it. UTIs are minor annoyancs -- the kidney problems caused by untreated UTIs are downright dangerous. Don't let it get that far.
After you get treated, make sure you do the following:
-- watch your hygene and that you're wiping front to back
-- urinate before and after sex
-- have a small glass of pure cranberry juice or a large glass of water after sex. (the cranberry juice has those wonderful UTI-battling ingredients, so it's good if you can do that, but a good amount of water will make you pee which should also flush out any bad bacteria)
-- avoid caffeine and very spicy foods (particularly if you get UTIs easily)
Having cranberry juice regularly helps. I have a glass about once a week now and it's been a good year or so since I had a UTI, which is very, very nice considering how frequent they were for a while. I've also had to cut down my frequency of eating spicy foods, which is sad because I like them so much, and I believe that's been helpful, too. On the days I do have spicy food, I also have cranberry juice. It's working.
Anyway... don't risk your health because of money. Protecting your organs is one of the few good excuses for going into debt.