If I remarry, can I still get Social Security from my ex husband?

Depends how old you are. If you remarry under age 60, then your survivor's benefits end. If you remarry over 60 the benefits can continue, and once you reach age 62 or later you may get retirement benefits based on the record of your new spouse if they are higher. More detailed info here: Social Security Online: Widows, Widowers & Other Survivors: Qualify and Apply