UTI - HELP

SpookWed143339

Hello lovely ladies, 

I am now 10 weeks pregnant and my Dr told me last week that I have a UTI. She prescribed  SULFAMETH-TRIMETHOPRIM 800/160 TABS for me take for 1 week. I filled the prescription and notice on the back of the meds it states " Do not take if pregant or think you may be pregnant". I freaked out and called my DR. and she told me she would always prescribe to her pregnant patience if they have a UTI. I still haven't taken the medication because i am still terrified. WHY would the prescription say that? I already had a miscarriage and i am so scared. 

Have anyone been prescribed this medication before while pregnant? 

 Thanks in advance!