Ive had some weird side effects too so dnt rule it out lol. My right hand twitches a lot, and i mean A LOT. It never did before. Saying that it might just be coindidence cos parkinsons runs dep in my family and this is one of the first effects....so i may be unlucky as i get older lol.
Hiya, don't know about the numb bellybutton but I can so relate to the floppy feeling, I've had that a couple of times when I've been particularly active, almost as if I've used too much energy at once?!?!? I've also noticed that if I haven't kept on top of my water intake, I feel quite weak and limp, so try and make sure I've had 2 litres by lunch and another 2 by evening.
Hope your bellybutton resumes feeling soon, lol