Hi edithb! Thanks for the kind words.  Snojones beat me to it with some solid advice - thank you snojones!!

I'll add that there are some picks that indeed have grooves/indentations that can help with this a little.  I switched to Dunlop Prime Grip picks that have ridges that help hold the pick in place a little better.

And just to echo snojones here, spend a bit of your practice time being intentional with your grip - maybe a few minutes of some easy strumming where all your attention is focussed on a relaxed but firm grip of the pick.  It takes time to burn it in so you don' t have to think about it as much, so keep at it!

Let me know how it goes!

Mike