This happened to me in my previous pregnancy. I was sick until 23 weeks and miraculously it stopped the day I quit taking the tablets!
This time I only took folic acid. Midwife recommended vitamin d, omega 3&6 and iodine sups too! I didn't bother and everything seems fine. She mentioned iron too, but according to the consultant my iron & haemoglobin are "lovely, lovely" so I haven't taken them either. Such a naughty mummy!