UTI wont go away after 3 weeks and 2 rounds of antibiotics!

I’m about 28 weeks and have had an ongoing UTI for 3-4 weeks now that hasn’t gone away from antibiotic treatment!! So far I have done two weeks of Macrobid antibiotic 2x a day, and now I’m starting Cephalexin 250mg antibiotics 4x a day for the next 7 days.

What possibly could be the next course of treatment if it doesn’t respond to these antibiotics?

Should I ask for IV antibiotics at that point??

I’m also worried the UTI might send me into preterm labor which I absolutely do not want to happen!!

I drink about a gallon of water a day (136oz every day) and I’ve been trying to have a huge glass of diet cranberry juice the past two days too. My OBs nurse recommended I could take cranberry pills, but I’ve never heard of those and she didn’t tell me a dosage.

I want my baby girl to stay baking as long as possible. What do I do/need to know about persistent UTI’s during pregnancy??

(I don’t want to google anything because I freak myself out from google).