18 month old straining

My DD is 18 months old. She has had regular bowel movements her whole life (1x if not 2x a day) but in the last 7-10 days has only had 3 or 4. She is also straining all the time like she’s trying to poop. She will suddenly stop what she is doing and pull her knees to her chest and bare down holding her breath. Her poops have been much harder than normal. We’ve tried more juice and fruits and took out cheese but nothing seems to be helping.

Anyone experience anything like this?