Update: MIL wouldn't give my son to my husband

So if you've seen my previous post, I received a lot of comments around how I should be suspicious of any supplementation happening with formula by my MIL.

I would never have thought my MIL would do this but its made me paranoid. When my MIL would come over to care for my son, she'd have a bag with her (like a tote bag, not a handbag.) I never thought twice about it before but now I am.

There's been zero signs of her heating up or using any formula in my house but I'm wondering what signs I should look out for in my baby. My baby just slept 6 hours overnight (very rare for him) and has only had a few poops (again, rare) His poop colour has been normal, yellow and green.

Is there anything else I should look out for?