What have you been eating lately? Bubba might have an intolerance to something you're eating. Two of my friends had dairy intolerant babies and they had to cut dairy out, very similar to what you're saying symptoms wise. I would recommend making bubba a GP appointment for tomorrow and if he does another very liquid poo, take a photo to show them In the meantime, start making a good journal for yourself so you can see if this links with any types of foods you're eating. Onions are a big one to avoid
I got prescribed baby gaviscon after doing the same with Infacol & Gripe water and it’s helped massively. I sit our baby up whilst feeding & then try keep her up for at least 10 mins after this has helped also x
Mucus poos can indicate an allergy like cows milk for example - you'd have to eliminate all dairy from your diet for a few weeks to test. Has baby been checked for a tongue tie at all? Our baby had one that we found at 7 weeks and having it released made a whole world of difference!
Not much help but maybe if he's still unsettled with wind after you've tried winding him hold him sitting up right after the feed for 10-15 mins as it can help with reflux if it is this. Apologies if it wasn't any help! My niece had a similar issue and we was told to hold her sitting up after a feed for 10-15 mins and she was fine after this x