Mommies I Need H-E-L-P !!!

So of course my son was like boarderline from being a premie (4lbs 15oz) at birth.
At His 4 month wellness visit they said he was almost underweight on the growth chart being that he weighed in like 11lbs. His doctor started him on rice cereal and at 5mnths it would be okay to move to baby food/ solids along with the usual Breastmilk (exclusively bf). We did so and at his 6month wellness visit this passed Monday he weighed in at only 12lbs and his doctor said he is now underweight for his age but other than that he's totally healthy.!
She said he needs more calories before she sees him again next month to weigh him And to try giving 2 jars of baby food each feeding. I thought wow that's a lot ! but if it gets him where he needs to be I'll try it. Nooow he's teething more and doesn't barely wants to eat 🙄 especially veggies! He drinks at most 2oz just spits it out.

Is there any method or strategy I can try to get him to eat more to try getting his weight moving up before our next visit??