Need some advice on weaning

My baby is 18weeks old and he has all of a sudden start too wake every 3 hours through the night wanting milk but drinking 6oz in one shot, at first I thought I was comfort but my doctor told me to start feeding him, so I bought mushed peas (suitable from 4 months up) and baby rice. The first day I fed him the baby rice and he kinda had half a spoon and must of thought it was his milk and went hysterical cause he couldn’t understand why it was different any way today I gave him some peas and well he ate the entire packet. Is that normal??? Is that bad??? I’m a first time mom and don’t have a clue how weaning works I thought he ate too much but he was asking for it and cried everytime I took it away he even cried when he finished it all but I didn’t have any more, please give me some advice 😂