I might be misunderstanding you, but it sounds like you are trying to finger the fretless bass in
exactly the same way as you would finger a fretted bass. On a fretless, your finger is actually replacing the fret as the point where the string stops vibrating, so in order to play in tune, it has to be in exactly the same place as the fret would have been.
Sorry if I misunderstood you! If I didn't, don't feel bad- I did exactly the same thing the first time I picked up a fretless!
