It’s not you. The site has been having trouble with the profile pics for a while. People who had one who tried to change theirs have lost them. I think it does work to set up a Gravatar elsewhere, but hopefully they will be able to fix the site system soon!
Here’s a link to a discussion about it. Help! Lost my profile picture and can't upload another one
I’ll tag @daybreaker, just in case in case things have changed.
Oh, and welcome to the Forum!!