Well, if you have been playing this few time fretless, I guess I understand why you're playing out of tune. I presume that your average ratio of correctly played notes goes around 20% if not less. It's quite normal, don't feel bad at all. There are plenty of exercises that I know to train the ear and increasing that ratio. No fretless player plays 100% tuned all the time, and in a way, that's the idea, but you must first to learn when you're are off key and how to fix it quickly playing without being noticed doing so. For almost 2 months of playing fretless I would say it's a decent attempt, but obviously there are too many things you have to do to play that song properly. A proper 'lesson' of exercises would be too long to explain here but I can give you some tips:
1- calibrate your instrument. No matter how good you are, if the bass it's not in shape, you'll sound offkey anyway.
2- compare different notes with a open string note to check your intonation - to do this you must be able to distinguish the different intervals (2nd, min-maj 3rd, 4th, 5th, 6th, etx), do this specially with octaves and you'll get used to the offkey notes.
3- deliberately play out of tune., to learn how exactly the offkey sounds both flat and sharp. This way, you'll know when you're flat or sharp and you'll know how you must shift down or up to get the right sound.
4- try to minimize the shifts from the right hand. Thy to play 'vertically, moving your fingers up and down thru the strings, but trying to keep a more or less fixed position on the fretboard. to go from bar#2 to bar#15 is too damn 'risky' on fretless, so try get those intervals with different strings.
If I have some more time, I can tell you more about it