Nope it stems from a sluggish CNS, the paresthesias, the lethargy as well the muscle weakness you report I'm very familiar with, in your case sounds like your thyroid slowed down or something.
Yes it could also be the HCG if your extra sensitive to endogenous progesterone stimulated by it. This will convert to a potent GABA agonist named allopregnanolone, which can induce the symptoms you describe, it basically slows down your CNS.