Good one day bad the next?

I've been battling nausea with this pregnancy. I'm 16+4 and I'm okay one day then the next day I'm throwing up everything. I've tried everything ginger, peppermint, doctor prescribed meds, and even shots to reduce nausea and vomiting. I've gained a little weight which makes me happy I've lost over 20 and gained back 6 lbs. but I'm terrified I'm not having a healthy pregnancy.