I had my thyroid and parathyroids completely removed in 2002, it had been enlarged for many years (since I was a child). It wasn't until after I had my second child (in 2001) that my TSH levels went wild and I went completely hypothyroid with a level of 142 by the time I had it taken out. I was completely miserable, tired, in a constant "mental fog", and felt like I could barely function. It took nearly a year from the first signs of symptoms (that I didn't immediately recognize)to get the initial lab work, get referred to an endo doc, get referred to a surgeon, get the operation, and then get my medications adjusted post-op so that I felt normal again.
When my husband and I were ready to try for #3 in 2003 we have no trouble getting pregnant. I saw my endocrinologist more often during the pregnancy to monitor my TSH levels and immediate adjust meds as needed. We had a beautiful and healthy baby boy in February of 2004.
Having been through all of this, I can say without a doubt that I would recommend going ahead and getting your thyroid out before it starts wrecking havoc on you. (I was told later that each time you go through pregnancy it can have a profound effect on your thyroid, often kicking you into hypothyroidism even without prior thyroid issues.) If I had known what I would be facing down the road and if a doctor would have suggested going ahead and having it taken out when it was just enlarged and not yet a problem, I would have jumped at the chance!
I hope this helps you. You can email me if you would like to talk more, ____@____.com luck!