I'm starting to take bacterial vaginosis tablets tomorrow. (monday) when will it be okay for me to have sex?

Best to wait a while: Best to plan on two weeks. For sure no sex until treatment is done (a week) and your symptoms haven't returned after another week. If sex is inevitable before then, use condoms for sure -- and you may help prevent recurrence of BV by continued condom use after that. I hope you were tested for STDs. BV is not an STD, at least not usually, but other STDs are more common in women with BV. Best wishes