advice on taking antibiotics during pregnant

I visited the lying in clinic for check up due to stomachache, paminsan minsanan na sakit ng tyan. Based on my lab tests, I have UTI daw. The doctor prescribed me cefalexin (antibiotics) and isoxsuprine para pamparelaks ng matress para hindi magcontract, both 3x a day for 7days. Am 13weeks pregnant. Ano po opinyon nyo po dito? Mejo takot po ako uminom ng antibiotic. Sino po dito ngtake ng antibiotic pero ok naman paglabas ni baby? Please help. Thank you.