How long ago was your surgery? You should be having regular blood work done, to make sure that the remaining thyroid is producing adequately.
Ask your doctor for TSH, Free T3 and Free T4.
I have had no bloods done at all. Prior to op a few weeks ago I did have thyroid done and according to those it was spot on . But since op nothing. Doctors just said home to heal and wait for results of tumour
Have you had any thyroid tests performed, since your surgery?
You need to have TSH, Free T3 and Free T4 monitored regularly to be sure your left lobe can produce enough hormones. If you've had labs done, please post the results here and be sure to include reference ranges, which vary lab to lab and have to be posted with results.
Thyroid malfunction can affect your menstrual cycle.