What Causes Skin Irritation And Bumps On Thighs While On Metronidazole For UTI?

Hi, I m 18 weeks pregnant. I seen my Bgyn two weeks ago. I got my test results back from my pep smear everything was normal no STD, but I did recently have a UTI, and another infection where I was prescribed METRONIDAZOL, he told me that is was not sexual transmitted. Well I took the medicine as directed until all gone, then this situation occurred days after finishing the medication up.For the past week and a half I ve been irritated between my legs. When I wipe I have this brown small ball like things. They don t have an odor but keep coming back and it sucks.I ve been married almost two months but we been together 10 years with 4 kids. Me and my husband aren t having sex and haven t since my Dr. Appointment but I have rubbed myself multiple times my hormones have been crazy. But for the past 5 days I haven t touched myself sexually because its been irritated and after I bathe its really irritated and I just wanna keep wiping it. Please help me. I just really want to know what this torn up tissue like stuff is.