Is my excessive sweating due to hypothyroidism?

Sweating. It's more common w/ hyperthyroidism. Do you take antidepressants? They can cause it. Check thyroid levels, and TSH . You may be running a little hyper on replacement t4.
Probably not. Excessive sweating (hyperhydrosis) is not usually caused by low thyroid. On the other end of the spectrum, hyperthyroidism can cause sweating and heat intolerance.