Brief Answer:
Try dietary sources of iron instead of iron supplements

Detailed Answer:
Thanks for asking on HealthcareMagic.

I have gone through your query and understand your concerns. Let me emphasize on the fact that breast milk is the best possible milk for a baby and there can be no alternatives for the same. Most formula milks are cow milk based and hence difficult to digest. Moreover they make the child more prone to complications and infections. Mother's breast milk is produced on the demand of the baby. Hungrier the baby, more vigorous is the suck. More is the suck, more is the amount of breast milk produced. Giving formula automatically reduces the demand of the baby and thereby the production of breast milk. All you need to do is to switch back to exclusive breast feeding and the production will increase automatically. All you need to do is to monitor the urine output. If the frequency is more than 6 times in 24 hours, you would know that the amount of feeding is adequate.

Now coming to your actual query about how to resolve the constipation. Firstly, iron supplements do cause constipation. I would insist you to get your blood hemoglobin level to check whether you need any further supplementation. Some of the best plant sources of iron are:
Beans and lentils
Tofu
Baked potatoes
Cashews
Dark green leafy vegetables such as spinach
Fortified breakfast cereals
Whole-grain and enriched breads

Taking these along with plenty of green leafy vegetables should take care of your constipation. Also make sure that you drink plenty of water. As of now you may benefit from taking isabgol husk (psyllium) with water at dinner.

Feel free to write back.

Regards

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