Sounds like it could be OHSS - did they mention the possibility to you? A certain amount of bloating can be normal, but a big jump in weight can be a sign that your E2 levels might be a bit high.
I'd keep your clinic informed of any symptoms, including weight gain or increase in girth. Take it easy and get plenty of fluids - hope it doesn't turn out to be anything to worry about.
Oh, and good luck for your transfer!