New born constipated HELP! 😤

Suniia • Hello , my name is Suniia I am 21 and me and my DH is expecting our second child May10th 2016.
My 1month old daughter has been constipated for 3 weeks. Having hard pebble bowel movements that is so painful to her . First she had bad stomach pains due to the formula she was drinking, now she's on soy and I understand with a formula change the constipation will start back up but I have tried natural remedies to get her to go per her pedi's recommendation. Bicycle exercises, stomach massages, prune juice with 1 oz of water. The prune juice worked for 1 day and she went great twice now she's backed up again. What can I do or buy? Her pedi recommended pedi suppositories but to cut it in half but I heard it gives babies cramps so can I use the liquid glycerin suppositories?