I gained about 4kg (I’m in UK just checked and that’s about 8-9lbs) like you I find my weight can fluctuate quickly, which makes me wonder if it’s fluid retention at least partly.

I like swimming too, it’s maybe not the best fat burn but I think it’s good conditioning and toning, I’m swimming once a week. If you have a bad knee can you manage stationary bike? Those are good for short burns!

Good luck and maybe check back in to let us know how you’re doing? You can do this!