Fetal Movement

I am 20 weeks and 3 days. We recently went for our anatomy ultrasound and we could clearly see our baby is very active. Even the tech and the physician said the baby was very active. Here is my concern; I still have not felt the baby move? I clearly felt my son move at 20 weeks. I was 26 when I was pregnant with him. Now I am 32...had a gastric by pass 3 years ago. Any insight?