I'm 15 weeks and 3 days pregnant. I have to take metronidazol. Can I take it with my prenatal vitamins?

No Flagyl Red Flags. Yes you can. Remember not to drink any alcohol, both for the pregnancy -and- the nausea and vomiting it will cause. Also, in case you are curious, there's no evidence that it will hurt little Johnny (or whatever the name is), but it does come out in the breast milk in sizeable amounts which probably wouldn't do any harm, as long Johnny doesn't hit the bars. If still worried, then switch to formula.
Separate but equal. The Supreme court of medical opinion suggests that the best declaration is "separate" your two pills by at least 4 hours for better absorption for "equal" treatment results. Preferential treatment should be given to the oral contraceptive pill taken first.