C.R.
I had the same problem with my daughter who is now 8 1/2 months. I have made all her food...and when she began to get constipated when I intoduced formula to her at 7 months, she began to get constipated. I now just give her one ounce of prunce juice to her formula, once a day. If things look good, meaning it begans to come out mushy, I stop giving her the prune juice for like 2 days.
I bought the prune juice from Whole Foods and Trader Joes. Hre doctor recomended it to her. Plus, I may sometimes dilute it with an ounce of water also. She has not gone a day without a bowel movement.
Good luck!