Oh hun, trust me, I know exactly what you're going through. T__T
I've had recurring UTI's since I was four years old, taken every antibiotic out there, and in the last week alone, have had at least three-four UTI's. I'm STILL taking antibiotics, but its not making a dent at all, and the urine that's trapped in my bladder refuses to come out.
It's likely you are, unfortunately. Taking them too regularly makes your body immune to them. T_T You might have to have IV rounds, like I probably will soon.. otherwise, the infection will just stay no matter what, and you don't want any damage to your bladder wall/kidneys. Have you had any damage that you know of?
You need to go back to the ER for sure. Tell them that the infection's gotten worse, and you've gone through those antibiotics. Demand tests, (you'll want to make sure there's no damage, and the reason you're getting infections in the first place..) and the IV treatment. Maybe it'll have a higher chance of working once it gets into your blood stream directly.
-virtual hug- UTI's are so uncomfortable, so painful. I'm sorry you're having one this bad. I'm the same exact position as I write this. I wouldn't want to wish it on anyone...
The only other thing I can recommend is plenty of water, rest if you can, and just definitely go back. I really hope you feel better.