So I want to marry Aela but shes not giving me the option. I was previously married however i killed her. I finished all the companions quests and so on but I'm still not getting to the option. Do I have to get a different Amulet of Mara or can I keep using the same one?

Any help would be appriciated.

you cant get remarried.

As Aphaea pointed out, it's impossible to remarry in the vanilla game.

She wouldn't want to marry an uxoricidal maniac anyway.

Yer ... she seems the smart one to me....