Hello everyone. My son is one year old and doesn't eat much at all, st…

Hello everyone. My son is one year old and doesn't eat much at all, still on formula milk, doesn't want any porridge, he might be able to eat some soup, mashed potatoes, because he's always constipated, he poops for 2-3 days once. I want to teach him to eat normal food, but it's winter now, and we only have front teeth coming out, he gets nervous and doesn't sleep properly at night (I'm worried about how he poops).