Well, all of those reasons apply in some way! I am about to be tested for thyroid stuff as I have also been suffering a horrid irregular heartbeat for the last few months, about the same time period as the jelly feelings! I'm definitely anxious at the moment, again, tied up with the heart thing (it's scary!), peri stuff and other issues at home. It's all such a weird tangled mess, everything seems to kick everything else off.
The jelly feelings are so much worse in the mornings....this is the time when I believe we have a natural cortisol imbalance so I suppose that theory makes total sense baby jane!