This sounds like your surgeon did a fantastic job of tightening the abdominal walls. You should feel it lessnen over time. The best way to avoid that feeling is to eat smaller meals throughout the day. This is a healthy option anyway. Good Luck!
Before you had your tummy tuck, your muscles were likely stretched out (rectus diastasis). You had much more space for your stomach to expand before you had your tummy tuck. After your tummy tuck, your muscles have been tightened (muscle plication) to help give you a flattened tummy. Now there is less space for your stomach to expand, hence it is not uncommon for patients to get full quickly or feel tight. This will slowly ease up over time as everything heals. Hope this helps.