new to recovery, my stomach hurts and IDK what to do

I didn't realize I had a problem until I started doing labs for my nutrition class last week. turns out I was getting so far under what I need that it isn't even funny.

I'm doing my best to fix this, but I honestly struggle the most with the sensation of feeling full. Like I ate a portion of rice, chicken, and bell pepper and I felt really good about it, but now like an hour later my stomach feels like it's having period cramps.

Are there any obvious causes or easy fixes? did I increase too much too quick?