24 weeks and uneasy stomach

So I’m 24 weeks and ever since 23 weeks hit, my stomach feels so off. It’s like a mix of feeling gassy, very full, somewhat nauseous, and constipated, on top of extreme heartburn.... an overall uneasy crappy feeling. I have been taking tums, eating right, exercising (I’m a high school PE teacher), and drinking a gallon of water a day. Besides having trouble sleeping and getting use to my growing belly, this is the only thing (knock on wood) that is making this pregnancy difficult.

Is it normal for my stomach to feel like this?? Are you, or have you felt like this so far? And did anything help relieve it?? I’m desperate.