I Have Been Taking Thyroid Meds For About 7 Years

I have been taking thyroid meds for about 7 years and been doing ok except the last 3 years I've felt like the meds are not working even after being tested on a regular basis well today I accidentally mentioned to the pharmacist that I was taking aleave at the same time as my thyroid meds and she said that that probably was canceling out some of the thyroid medication to my body could this be true I knew I was not supposed to eat when taking my medication but did not no I could not take other medications the same time with the thyroid meds