Password for my iPhone and iPad

So today I wanted to change my password on my phone, and I noticed that I had forgotten my password. I though it was weird because I had been using it, I brushed it off and tried the password on my iPad only to find that it also wasn't working. I thought maybe it was because I use Face ID, but then I remembered that sometimes I used my password because Face ID didn't recognize my face. I don't remember changing it to anything else and if I did I only changed the password on my phone not my iPad. So know I'm locked out of both my phone and iPad and I don't know what happened or what to do. Does anyone know about this?