Excellent melody, and really excellent harmonies! Memorable treatment of these. Your singing definitely puts me in the mood of some pretty classic '60's pop, which I quite like.
For me, the background electric guitar got a little samey throughout the piece - you might drop it out more.
And the snare sounds like you have really spent time on the reverb, but it kind of gave me a "recorded in a stairwell" feeling, which I could see fitting the mood/era of the piece (1960's) - my ears in 2015 wanted the snare to be drier.
very nice work, I can totally relate to "I wrote this years ago, just getting around to recording it" !!!
cheers.
-Tom