Need advice.

So my son's pediatrician said to start him on whole milk and change bottle to a cup. (Jan 11 so I did, still on bottle tho)

He does eat solids but not like a whole 3 meal. He picks at it. Has a snack here and there. And water.

I'm trying to cut back on his whole milk since he keeps having yellow poops right after a bottle.

I took him to urgent care and they said he might be having too much milk.

I feel like just changing him back to formula since his not eating enough solids.

I'm still learning here. I feel like I'm failing with him. I'm also due next month with my 2nd so the stress is getting to me. Idk what to do.

I try to feed my son food but he just isn't getting full.

Help. Please