Constipation to diarrhea in one day? *TMI*

This morning I felt like I needed to poop so I sat on the toilet for a while but couldn’t poop. Then about 2 hours later I really felt like pooping again so i went to the bathroom and managed to get a little pebble out. Then again a couple hours later I needed to go again. This time I managed to actually poop but it was pretty firm and hard to pass. Like clock work I needed to poop again about 2 hours later and this time it was softer and easy to pass. Now I just went again and it was almost liquid. Why would I go from one extreme to the next in only 9 hours? And I’ve pooped so much in a short amount of time. I have been regular so I shouldn’t be all backed up?