Try sub-dividing your beat, so instead of counting ' 1 2 3 4' count '1 & 2 & 3 & 4 &' instead. Then before you even try playing anything on the bass, get comfortable clapping thru the rhythm. It can help to write (in pencil) '1 & 2 &...' above each bar so that you can see where each note lines up against what you're counting.