Try this, it's something I tell my students to imagine.
Set your metronome to a reasonable tempo, 60 BPM or somewhere like that. Listen carefully to it clicking, and visualise a ball bouncing in time to the click. It's hitting the floor on the click, at the top of its bounce is the off beat. Concentrate on this, and really get it into your mind.
Tap your foot along to it, clap along to it.
Pick uo your bass.
Practice playing quarter notes along to the click, getting your notes on the click.
Practice playing eighth notes, again get your first note on the click, the second is at the pinnacle of the ball's bounce.
Sixteenth notes you add another half way up the bounce, and half way down.
Get a good teacher too.