I Had My Thyroid Removed Twenty Years Ago. I Am

I had my thyroid removed twenty years ago. I am currently on Synthroid. The last three years my thyroid numbers have spiked and plummeted, my doctor can't seem to get it regulated. I researched my problem and there were several meds and supplements that could be interfering with the Synthroid. I also have had itching along with the spiked thyroid numbers. I stopped taking the supplements and meds; I haven't had my blood tested since March 6th, I'm due to have it tested on May 4th. Do you have any thoughts?