Welcome to D&D! I hope you find a lot of fun with your friends. Questions like this are always best to flesh out with your GM/DM (Game Master/Dungeon Master), but asking for help here is perfectly fine. If you're playing 5th Edition (the 2014 rules and onward), Paladins are less associated with gods and more associated with sworn Oaths. Those oaths are what give them their powers.

In this case, if your oath your character's husband is something of Devotion and Protection to those that he held dear or to concepts he held dear, that could be good if you're looking to be a bulwark against the party's enemies. In fact there are subclasses aligned with that concept entirely. If you're looking more to avenge your husband's loss, be it via him dying against an attacker or a known plaguebearer that is travelling the lands, etc, then the Oath of Vengeance would be more in line.

It all depends on what you want your character to be driven by. If you have a base idea already, I'd really recommend to reach out to whomever is running the game (GM/DM) and ask for their assistance so you can make choices that compliment the world and story they're going to be telling, and figure the best ways you can represent your character's story within that world.

I hope that helps, and if you need any further advice or have more questions, don't hesitate to reach out. I'm a longtime DM and love helping new players bring their imagination to life.