Important things first, perhaps you should use an audio editing software to normalize the volume of the music. The listening experience definitely gets better the louder the song is from the start (although you don't want to clip it unless you're into that or it's absolutely necessary). I recommend Audacity for this since it's free.
Other than that, I'd say it'd be favourable if the song had more variety than the single repeating melody pattern you got there. I mean you could compensate by adding more instruments or making it sound more varied but at the moment I keep hearing the same three tones, and by the middle of the song it becomes... well... to be blunt: boring. I also feel like the last drum bit felt out of place, or left the song sounding incomplete.
Nice song though, and congrats on your longest song!