Diclegis still needed

I'm 23 weeks and 2 days. I've been taking Diclegis for horrific nausea since week 7. I was taking it 3 times a day. But now just take it at night. I misses my dose last night and boy have I paid for it today. I've had boughts of really bad nausea all day. Even when eating. I'm just wondering if it's normal to need the Diclegis this far into the pregnancy. Shouldn't the nausea be better by now???