Hey mama,
It is normal and only natural to feel tightness at the ribs and especially just under the breasts. Baby is growing and as she does, there’ll be a lot of pushes upwards towards the chest, and downward pressure.
I remember there were times where I could hardly catch my breath because my diaphragm was squished!
It’s important to do deep breathing during this time to keep circulation up and also, to do relaxation exercises.