Can someone help out?

Hello. I have a few questions. Recently I've been having irregular periods. In July, I missed my period and got it on August. This past September I didn't get it an I should be gettin it in a few days. I took a pregnancy test and came out negative. Also, I had some weird brown stains with an ammonia kind of smell on my underwear. I had something like that last year, And used a medicine call Metronidazole so I started using it again this time. After the second day of using Ingot some weird discharge that looked kind of like meat and now, it's like brown and blood looking things coming out. Should I be worried? I don't understand what's going on with my body.