5month old constipated

A few weeks ago my little girl was constipated, I took her to the hospital & they prescribed lactulose and that didn’t work so they gave her a suppository. They said could be her formula which I thought was weird because we hadn’t switched it at all.

By the morning she had pooped and everything was good up until yesterday, she randomly got constipated again.

This time I caught it early and gave her the medicine along with a suppository and it’s not working at all. I haven’t given her any solids and I’m making her bottles as normal.

Why is this happening? Is this normal?

I feel so sorry for my poor girl, if she doesn’t poop soon I’m going to bring her to the hospital again.