susan
A goiter is a loose term for an enlarged thyroid.There are many kinds of thyroid nodules and diseases.An endocrinologist will be able to diagnose what kind of problem you have, so you are on the right track to be seeing a specialist.It sounds like you might have an underactive thyroid since you said you are tired and your periods are off.Also it sounds like there is a nodule(growth) present.There is medication, called synthroid which can restore normal thyroid function.Doctors have very good treatments for thyroid disorders and once they diagnose what's going on, you feel better.Good luck!