How recent is recently? Last couple days, weeks? You mention food poisoning as a possibility, so I guess it isn't long term...?
I had the same kind of thing going on a couple weeks ago, the weird acid burps and then a few days of vomiting.
If it is the chia, is it from a new source? (I have no idea if that could matter, just a thought.)
Personally, as I stopped eating so much yogurt, I started taking a multi-strain probiotic instead. Maybe that would help you?
Dunno what else to suggest. Whatever it is, believe me, I'm sympathetic.