Hello girls, can you tell me what to do? The baby is not gaining weigh…

Hello girls, can you tell me what to do? The baby is not gaining weight from milk, I'm on a diet and my stomach hurts, it burps in my tummy, but we hold back and can't go to the toilet, we're struggling, we want to go to the bathroom, she falls asleep in her crib for 5 minutes, then she sleeps normally, then she starts wheezing, I'm going crazy soon.