Heart palpitations

So before I got pregnant I would have random episodes of sinus tachycardia and heart palpitations but since I've gotten pregnant my heart palpitations have doubled ten fold and it's driving me nuts! Almost daily I get them and they will last half the day. They will sometimes stop for a bit then start right back up. I have a cardiologist but the meds he wanted to put me on for them he couldn't because they aren't safe during pregnancy so he told me to take magnesium but it's not really helping and I drink enough water during the day. I'm losing my mind with them and I feel like Im just waiting to have a heart attack. 😩