totally been there. i spent like a month fighting travis picking before it clicked. the thing that helped me most was slowing waaay down and just doing the thumb pattern on its own until it was completely autopilot. like embarrassingly slow, just boom-chuck-chuck on repeat while watching tv.

once your thumb is on cruise control you can start sneaking the melody notes in with your other fingers. also Dust in the Wind is a great practice song for this - the pattern is repetitive enough that your hands eventually figure it out on their own.

hang in there, it really does just click one day