Mixed feeding with formula and breastmilk QUESTIONS

rainbow0718

My 1 month drinks 1oz of Enfamil Gentleease once a day & the rest of his feedings is breastmilk. He constantly strains to fart & poo for hours, sometimes he'll cry a little while doing it & have trouble sleeping through. I have to massage him for 30minutes+. He poo at most once a day and it is a thick yellow or green poo like peanut butter consistency. I wanted to see if it's just him or the formula so one night I didnt supplement formula. I notice a change instantly. On breastmilk alone, he grunts & strain but he is so calm & easily passes yellow, seedy, and watery poo. He also sleeps through the night. He has been on Gentleease for 3 weeks. He poo w/o struggle at first. Now, he just seems uncomfortable all the time but it's the only milk he does well on. I've tried Similiac advance, Similac Sensitive and regular Enfamil. With both similac, he is extremely fussy, gassy, spits up a ton & he grunts so loud and cries everytime he tries to poo. With regular enfamil, he spits up a ton and he also is very gassy with trouble pooping. Is it just him getting used to the formula or is he not responding well to the formula and I have to switch to maybe a soy based one as I've heard it is easiest to digest? How long does it take for a baby's digestive system to get used to formula? Will he eventually stop straining and grunting to poo this thick consistency? Will this thick consistency change once he gets used to the formula? I AM AT A LOSS 😫 I supplement with formula so we wont have trouble switching for when I go back to work and so I can have babysitters when I need to run errands. When I pump, it makes me have oversupply. So when he eats, he chokes on the milk as it is fast to come down no matter what position I put him in. So, pumping is not an option for me. I need tips, advice, no mean or judgy comments pls. FTM 

mamanbebe

Formula slows down digestion and changes the bm consistency. If you’re getting daily or every other day you’re doing well for this age when the digestive system is really immature. It will never be the same type of poop as breastfeeding but gas and strain should ease up a bit over time.