He is only wanting to eat pasta and tomato sauce, porridge, and toast. Some days he does not want much to eat at all. He has even gone off jarred food which he used to like a lot (sludge, as we call it!) and would have when he was off food.
I have not checked his weight for a while so am going to get him weighed this week but am worried he is not getting enough food.
He was until 16 months or so breastfed, and won't drink cows milk consistently, will drink from a cup a few oz but nothing significant.
Is it ok to just feed him pasta and porridge for now?
20 month olds have very small stomachs. They benefit from a 'little and often' approach with a combination of tempting snacks, old favourites and new foods. Large meals can be offputting. Anxiety from a parent can be the same. Bump up the calorie content of his food by adding oils and butter where possible if that's a concern. Try pureeing some lentils into his pasta sauce or stirring an egg into his porridge so that there's a little more protein etc. Does he eat at the table with you and the rest of the family? 'Monkey see, monkey do' is another tactic. Does he eat with other little ones... similar rationale.
If he's healthy, in the right area on the growth charts, cheerful, not listless or coming down with colds all the time, he's probably fine. But if you're worried, always talk to your HV or doctor. A friend's toddler DS, after years of concern about how little he ate, was finally diagnosed with an ENT problem that made it very painful for him to eat or drink. They'd spent a long time thinking it was their fault he didn't eat when it was a medical problem all along. Not saying there's anything similar going on here but always get things checked if you're worried.