Newborn constipated

cole • 3 Girls my prince will Arrive SOON 🥰

So I give my son breast milk and formula.. haven’t been able to produce as much breast as he have been getting formula. He haven’t had a BM in 18 hrs so I gave him 2 oz of water and he had two BM within that next 3 hrs now he is hungry and I’m concerned do I give him formula or water because I’m trying to unclog him !? He only 1wk so I’m scared with the water ?