Diclegis morning sickness pill

So I'm 19weeks 1day pregnant today. I've been on Diclegis since about 8weeks. I tried stopping the pills when I got to 13weeks but got extremely sick the first full day without them and was put back on them. My doctor said to try and stop them again at 18weeks. So this time I weaned myself off them rather than stopping cold turkey. This past Monday was a full day without them and Tuesday morning I woke up and was extremely sick all day long. Couldn't keep anything down at all. I'm wondering if this has happenedto anyone else? Is it normal to still be sick at 19weeks? I'm wondering if I'll have to be on these pills my entire pregnancy and if that's okay?