Not producing much milk

Sheila
So in the first week of my pregnancy I produced so much milk that I couldn't stand how bad my breasts were hurting. And sadly I started slowly reducing the production of milk which made me turn to also feeding my daughter formula. Enfamil gentlease to be exact. And I cry because my poor baby doesn't poop as often as before and it's hurting her. She cries when she tries to push. I don't know what to do. I'm heartbroken that I can't give her all the breastmilk she wants. I hate seeing her in pain and not being able to poop until late at night. Today was the first day she wasn't able to poop. She tried and tried but nothing came out. I wish there was a way to help her with this constipation but the damn iron in the formula is what's causing the constipation. I want to try an organic formula but they are too expensive for me to afford at the moment since I'm not working at the moment and just barely making it with the disability money I'm getting every 2 weeks. I'm hurting so much right now and just need to vent it out. :(