When I go on sims my previous families have gone

I created a family, spent a lot of time on it in one game then I’ve come on a few days later and the family is gone completely? I can’t go on manage worlds until I’ve created a sim and even then they’re no where. My families aren’t saving so I’m creating sims and stories knowing the next time I go on they’ll be gone! So frustrating. Can anyone help? I’m not very technical so any help would be much appreciated