Agreed to raphjd's comments above, with particular attention to whether the domestic partnership law legally entwines you in any financial aspects, present or future. As well, was this partner named in your medical Living Will? For receiving the disposition of your remains? Is he in your estate's will? (And if you don't have those documents, for heaven's sake, get them drawn, no matter your age.)
The formal dissolution of the domestic partnership is a prudent step to protect your assets and formally reestablish your "single" status. It will likely require filing the related paperwork at City Hall or other state agency. Consult a lawyer in the city/state where the partnership was signed – you may both need to "co-sign the divorce," fun, fun -- and then know that you're truly free and clear.