Soy intollerance?Which foods not safe?

Aiden is exclusively bf, and seems to be intollerent to soy in my diet.
Isla had dairy allergy/reflux/eczema and multiple other food intollerences which she fully outgrew by age 2 yrs, but had no problem with soy and still has soy milk rather than cows, but can have small ammount of dairy products with no problem.
Aiden was getting reflux and was very unsettled until
I stopped having soy milk. I have since tried to have it again on 4 different occasions weeks apart, 2 diff brands, and each time he has had 24 hrs of screaming in between sleeps, farting lots, very unsettled.
So I havent been having soy for about 2 months now and hes been good. I dont drink cows milk, but do have other dairy products, I dont have choc or caffine/ no spicy food/onions etc.
This week Mum made soup, I had a bowl and he was very unsettled- there was only 1/2 an onion in the whole pot plus meat/veges that I usually eat and one of those dried soup mix packets with the dried peas/barley and stock powders in it.
So I ate it again the next day, and he contined to be even more unsettles, farting almost constantly day and night and obviously uncomfortable with it too. I got Mum to check te soup mix packet and it contained soy. Would have been such a small ammount in that whole pot of soup, and I only had one bowl each day for 2 days. Would it be likely that it was the soy, or could it have been the barley or other dired grain in it?

Should I avoid all things with soy like soy sauce and soy&linseed crackers and bread or do they contain diff types of soy?

Any help greatly appreciated! Im clued up on dairy allergy, but no idea about soy!
TIA!

I am soy free, and have tried just a tiny bit in the bottom of a glass on 4 diff occasions since then and hes been very unsettled for 24 hrs each time.

Whats soy lecithin?

We are almost soy free here as well. Definitely should be for myself alone.

Soy flour is also in bread as well

I believe soy goes through my bm. My boy didn't skin prick to anything but he has reactions when I have soy, although they are more slow to build up & slow to get rid of.