They put me on Amoxicillin. For the remainder of my pregnancy because they think the bacteria is sitting in my kidneys. And I'm 33+2.
I agree it sounds like a yeast infection.
Antibiotics often cause yeast infections, because they kill off beneficial bacteria in your vaginal tract. When you're healthy, yeasts and bacterias in your vaginal tract (called "flora") keep each other in check. When you're on strong antibiotics for a UTI it wipes out all the helpful bacteria and the yeast take over.
Tell your doc and they will prescribe something for yeast.
Itchy and swollen doesn't sound like a uti to me. It could be bacterial vaginosis or a yeast infection. I'm prone to these conditions and life is hell for me. Some doctors misdiagnose because vaginal problems are so similar. I don't know about the back pain or contractions. That might just be because you are further along?