Hurts to urinate, UTI is back, why does it keep coming back?

I have a UTI and I know it is. I had the UTI before while I was pregnant it was really awful! I was in so much pain. When I went to the doctors May 17 they said I had a over 200 blood pressure and was sent to the hospital. I had preeclamsia. May 18 I had my beautiful daughter at 34 weeks and she was very healthy. I was in the hospital for a week and they treated my high blood pressure, found out that I'm anemic, and hyperthyroidism came back high again. Plus I was treated for my UTI. My daughter is now 3 weeks and UTI came back, I don't understand. I wipe front to back, shower, I take care of myself. This is my second day getting it back — why does it keep returning?