Husband has insurance (HDHP) from his employer (now retired). I am covered self-only under his plan even after he goes on Medicare during 2017. Can he only contribute to his HSA for the months covered under the HDP as family & none for the months I am covered as self-only? Do I need to contribute to my own HSA for the months I am covered as self-only under his HDHP insurance?
Your husband was no longer eligible to receive contributions to his HSA (from him or from you) when he went on Medicare.
You, however, were eligible to contribute to his HSA until he went on Medicare and to your HSA all year.
You need to be sure to fully answer the questions in the HSA interview (Federal->Deductions & Credits->Medical->HSA MSA Contributions). On the screen with the heading "Was [name] covered by a High Deductible Health Plan (HDHP) in 2017?", you need to answer "Yes" to the question of having HDHP coverage for at least one month, then when the three new lines are exposed, you need to answer "different type of plans at different times of the year". (See screenshot below).
Note that each of you will answer these questions, for each HSA.
This will help TurboTax accurately calculate your annual HSA contribution limit.
Also note that your husband's HSA does not cease when he started on Medicare; only his ability to contribute to his HSA stopped. If there is still money in his account, he can continue to use it for doctor's bills and prescriptions until the funds run out. Note that this includes reimbursing himself for premiums withheld on his Social Security check for Medicare (note: for Medicare only, not for Medicare supplements).
But stewie, dmertz is correct. Before you make the final entries in TurboTax, you should ascertain whether or not you are still on a Family plan in your HDHP or whether you were switched to a Self-only plan. It will make a difference as to the final annual HSA contribution limit.