My FSH was 8 last month now it is 39!

My RE wanted me to do another CD 3 test since my results in March only showed an FSH 8.7 but no estradiol was done.  OK, last week, I went to the lab so they could do a CD 3 test so the results of FSH and estradiol will be sent to the RE's office.

Got a call today.  Lo and behold, my FSH is 39.4 and my estradiol is 24.4 (range < 50).  How did this FSH change this drastically?

One thing I know has changed is that right after I did my CD 3 test in March, I had changed my thyroid medication from Synthroid 50 mcg to Tirosint 50 mcg.  Guess what?  I was late almost 3 weeks for my period!  As soon as I took the Tirosint my period went from heavy to non-existant in March!  I had to get off Tirosint and go back to Synthroid to get my period.  So when I did my CD 3 test in late April it was during my period that came 3 weeks late!

Anyone have any clue on what may be going on? Can an FSH fluctuate this much?

TTC is so stressful!