I recently started taking Liothyronine 5mcg twice daily as well. I am also experiencing nausea daily. It's been about 2 weeks. I am hoping that this subsides soon. I also started taking Formin (natural Metformin) around same time. There is some information that says diabetes medications may interact with Liothyronine. I am keeping close tabs on my symptoms and reporting back to doctor soon. Hoping this is just temporary.
Adding a total of 10 mcg of T3 doesn't sound like too much, but it is the equivalent of somewhere between 40 and 60 mcg of T4, so it is a hefty increase. It might be better for you to back off to only 5 mcg for 4 or 5 days, and then add the additional 5 mcg. That will give your body some time to acclimate.