Diarrhoea

My 3 month old LO has been having diarrhoea for 9 days already. It started last Thursday (16Jan), we brought her to the PD and got Hirasec & Probiotics.PD diagnosed as virus infection. He also said she's if still not well, go back on Monday. PD mentioned to only feed her BM as they're lots of antibodies etc. Monday (20Jan) came & her condition still didn't improve. Went back to the PD & got the same meds. Today (24Jan) is the 9th day & she's still having the runs. Poop wise is yellow & watery, she poops about 7-8 times (big poops would be 3 times a day). She's still very happy & cheerful, smiling as well. She doesn't seem to be in pain. We're not sure if she might suddenly be lactose intolerance or what. Anyone experience similar issues?