The weight gain in particular has me thinking OHSS... I had it really badly with my first two cycles and couldn't transfer. It gets worse with pregnancy. My third cycle I was well enough to have a transfer, but I still developed OHSS - this time it set in when the embryo implanted. I woke up on the morning of my blood test and had to go up a size in clothing because I was so bloated. By the time the OHSS bloating went down, the baby bump was taking over. If it was just gas, I wouldn't expect that much of an increase in weight.

All I can suggest is rest as much as you can. If it is OHSS associated with a pregnancy, you can look forward to it not really going away for a few weeks.