Ugh, every post I've started in like the last 6 months is to do with eating or weight

So my son (17 months) goes up and down in terms of eating and he's in a major DOWN phase at the moment. He seems to really hate his high chair and will pretty much eat nothing at home with us, but will happily eat his whole lunch and seconds at daycare. I think we've created a negative stressful eating situation for him at home, and now I don't know what to do about it.

He is low on the growth charts and when he was 11 months he dropped off completely so we're always stressed about him getting enough. When he refuses to eat my stomach ties up in knots and I have to constantly hold back tears (in fact, I'm holding back tears now just typing this). I KNOW he can pick up on my stress and that we've gotten into a vicious cycle, but I don't know what to do to stop it.

Does anyone have any advice on how to minimise my stress and make mealtimes more enjoyable? We do all the usual stuff - eat with him if at all possible, small portions on the plate, let him play with his food, have a set time for eating, minimise distractions, etc. I feel like I'm approaching the end of my tether and I'm doing dinner alone the next 3 nights, I'm already dreading it.

Help, please!?