I like the melody of this piece but there's several things that are a bit off.
The most drastic and offset if the mismatching of the harmony. I haven't learned enough music theory to tell you exactly what it is thats messing it up but its like your not even quite hitting the notes, your hitting like odd semitones. And that bass harmony you've got going is slightly off too i think.
Another big thing is the portamento you have between the notes. Its awkward timing and makes it sound out of tune during each switch. Try to reduce the time it takes to switch notes, and don't play while your switching. Basically just enunciating each note. If your going for the legato, you need to make sure that its a steady slide.
The last thing is just your rhythm. Make sure you play with a metronome. Its not drastic but you fall away from the beat a few times. It's especially noticeable in the bass harmony.