Severe cramping at 21 weeks

For the last two and a half hours I've been having cramping that feels like mensural cramps with a lower back ache. I've tried changing position, drinking water and nothing's giving me relief. Should I continue to wait it out if they aren't getting anymore severe? I'd hate to go to triage for nothing.

I also think I have the start of a yeast or bv infection so I treated myself with monistat today and have an appointment with the OB tomorrow. Wondering if this could be related to my cramping.