I don’t think I should be feeling like this

So I still work a full time job give or take days I’ve been missing which is kinda like atleast two days a week bus anyways besides the point I’ve noticed when I’m like walking too much even grocery shopping my stomach is extremely in pain. Like I feel like it’s gonna fall off. This is my second kid but it’s to the point I gotta squat in the middle of shopping because it hurts so much. Usually I wear a pregnancy belt but that only takes off a little of the uncomfortableness. My job I’m mostly sitting but if I’m up a lot it’s terrible. Anyone know why this is happening ? It’s hurts so much .