I can relate. I’m extremely FODMAP-intolerant. Onion and garlic are the bane of my existence, especially since they’re in literally every ready-made food that exists.
If you haven't tried the Enzyme supplement Fodzyme I can't recommend it enough.
Ever since I started using it I can (mostly) freely eat foods with garlic and onions as well as a host of other things.
It doesn't work on everything, but I have been ordering it since April and I am no longer reading every label on everything to avoid being sick.
Everyone is different so there's no guarantees on what will work for you, but I've been telling everyone about it (mostly because people always ask what I'm sprinkling on nearly everything I eat).
I get the brown jar because the individual pouches are a rip off, but it's less of an investment if you want to try!
Fodzyme is an enzyme that breaks down certain FODMAPs, particularly fructans which are found in onions, garlic, and wheat. There is currently only one other product on the market that breaks down fructans that I know of and I think you have to be a clinician to buy it. Fodzyme is pretty expensive and works so-so for me, though a lot of people seem to have good results with it.