Dr's tend to want to put people on 1,000 other drugs to cover over the symptoms caused by low thyroid BEFORE they ever prescribe Thyroid. At least that seems to be the general consensus.
So my initial thought was that if the Dr said you need Thyroid before several other drugs you most likely need thyroid.
Please post your results. If you don't have your lab test results ask the Dr for it, by law in the USA they have to provide you with the results. Folks here can help you more with knowing the lab results.
Do you have the results of the lab work your doctor used to diagnose you hypo and put you on meds?
There isn't always a familial connection with hypo.
How much Synthroid do you take, and do you have results of recent thyroid lab work? If so, please post with reference ranges (they vary lab to lab and have to come from your own lab report.
Do you know the cause of your hypo, i.e. have you had antibody testing to see if you have Hashi's?
Did you have any hypo symptoms before starting meds? Weight issues are only one symptom.