The flutters/weight gain could be a number of things. The best thing to do is consult your dr about this. You've already had a u/s so an intrauterine pregnancy has been ruled out so I seriously doubt there's a viable pregnancy there as your hcg levels are bottoming out. I wish I could be more help - it honestly sounds like your hormones are out of whack.
First off, you are not crazy!! After m/c, your body does all sorts of strange things as it readjusts. My system is completely messed up, gas is one of the things, and I will spare you the rest of the details..
However if you haven't had a normal period since your m/c and it was in May, I would schedule a Dr.;s appointment. Everyone is different, but typically you should have a period within 5 to 6 weeks. I had a D&C on June 1st, and have just finished mine. They may want to do a blood test and another u/s just to make sure nothings left, or you may need to take something to "kick start" your period again.
I am sorry for your loss, although I am glad to hear you are handling it so well. Good luck to you!