Sorry to hear your suffering morning sickness so bad. I work in a pharmacy and I use a website that tells you everything about medication it's side effects if ot can be used in pregnancy and so on and this is what it says;
Promethazine has been assigned to pregnancy category C by the FDA. Several retrospective studies have suggested that there is no increased risk of congenital malformations in humans with the use of promethazine in pregnancy. Promethazine has been shown to impair neonatal platelet aggregation when given during labor. There are no controlled data in human pregnancy. Promethazine is only recommended for use during pregnancy when benefit outweighs risk.
I'm currently pregnant with DC2 and have been medicated with Stemitil and Phenergan (separately). For DC1 my GP (male) was very unsympathetic, he would say to me 'a little bit of discomfort is natural you know' when I was throwing up 12 + times a day. I was constantly ketotic, dizzy, fatigued, my teeth crumbled and I developed shingles I was so run down. It was the loneliest time of my life .
My new GP who is supporting me through this pg was horrified! She has said anything more than x3 vomits a day is a cause for concern and while no medication in pregnancy is the gold standard I had to be realistic and untreated sickness could lead to low birth weight or ante / post natal depression. Take the help you need and don't feel guilty. HG is soul destroying, hope you feel better soon.