Having trouble eating at 21 weeks.

Lori
I am 21 weeks 4 day. I had horrible morning sickness in the begginning. I catch myself not eating well into the afternoon. Sometimes as late as 1 to 3 pm. I am just not hungry. I try to force myself to eat and I just cant. I take my prenatal daily. When I do eat it just is not a lot. I try to eat things high in nutrients when I do. This is my 3rd pregnancy and I gained well over 15 20 lbs in my first 2 by now. I'm not losing weight but I have only gained maybe 5 lbs. Baby had perfect measurement at the 20 week scan. Does any one think maybe Ensure meal shakes may help me? I will be asking Dr at next visit. Has anyone else had these issues?