Been taking levothyroxine 137 mg everyday for almost two years. constantly gaining weight - +100 lbs since i had my thyroid removed, easily irritated, no sex drive. every doctor tells me that my levels are fine. i feel like i'm going insane?

Because Levothyroxine is a hormone and it interacts with other hormonal systems (reproductive hormones, adrenal hormones, insulin/cortisol), a thorough evaluation is warranted. Talk to your Endocrinologist and request a full hormone workup including estrogen, progesterone, testosterone, insulin and cortisol. Your symptoms are probably due to problems with the other hormones.