I'm 15 weeks pregnant & diagnosed with UTI. Doc prescribed Norfloxacin, but everything I read says it's not suitable for pregnancy? What is most safe?

Call your OB MD. This is a question you should be asking your treating OB MD who gave you the Rx, not here.
UTI and pregnancy . It's important to treat urine infection in pregnancy. Nitrofurantoin or amoxicillin are preferred drugs as they are safe for baby . Norfloxacin is category C drug and is not preferred unless there's no other choice and risk of not prescribing is way more than side affects. .
UTI in pregnancy. Don't take norfloxacin. Nitrofurantoin is safe in pregnancy if u are not allergic to it.