I'm pregnant with a bad headache. If I don't have 2 extra strength Tylenol (acetaminophen) (500mg ea) can I take 3 regular strength (325mg ea)?

Yes. It's safe to take Acetaminophen during pregnancy, but it's not recommended to exceed more than 3000 mg a day. It's also advised to avoid taking Acetaminophen frequently unless the headache is really bad, otherwise, you may develop over-use headache. May try relaxation deep breathing, rest in a dark quiet room, or simply ice pak.