Black out spells?

Hi everyone. I was wondering if anyone has ever had issues with their heart racing spells. Where you end up getting light head and feeling faint? I'm 15 weeks with baby #2. Never had any issues with my daughter. But its getting to the point i can't take a shower or get ready without blacking out. My obgyn gave me a low blood pressure medicine because my bp and pulse goes up right before i start blacking out. But now my resting bp is getting really low. I have no idea what is going on, just seeing if anyone else has this problem.