Ah, that sux.....sorry. However, I'm pretty sure you'd be a good candidate for catheter ablation if you consulted an electrophysiologist. It would be worth maybe seeing two of them and deciding which would do best.

The fluid in the lungs would have little or nothing to do with your previous surgery, unless it failed to repair the mitral valve. Instead, with AF, and if it's persistent or permanent, you are getting less work out of your heart, maybe than before (you say you're feeling even worse!). Your lungs and kidneys need good blood flow, as does your brain, to work well. Both of those can let you slip into pulmonary edema (oedema in the UK :-D). By any chance have you noticed your feet/ankles pinching inside slippers or shoes as the day goes on? They look and feel swollen?