An acoustic version I came up with by ear. Might be slightly off, but it fits well.

Intro: B, F#, E

BLet (x2444x@1)me start by saying sorry

F#I (244322@1)know I don't tell you how I feel

EIt (022100@1)takes enough to say I want you but that's not what you need

(Play this pattern for all the verses)

C#m (x13321@4)                                                               AI'm (x02220@1)the last straw on the camel's back away

E B A
From saying those three words

B (x2444x@1)                                                  F#I'm (244322@1)putting a message in this song

EAnd (022100@1)I'll get everyone to sing along

B.                                             F#Just (244322@1)to let you know how I feel

EA (022100@1)valentine on mp3
Yours forever, less than three

B (x2444x@1)                                                                                     F#Take (244322@1)the distance from the depths of the deepest ocean

ETo (022100@1)the surface of Pluto                         C#mAnd (x13321@4)multiply by as far as you can count

AAnd (x02220@1)you'd still be nowhere near

EYou'd (022100@1)still have no idea

BHow (x2444x@1)much I want to hold you



And that's it! Repeat the verses and choruses, add some variation, but those are 
the chords to the fantastic 'Less Than Three' by the wonderful Eddplant!