I can relate!  I have a 3 year old son who is only 27 llbs (okay maybe close to 26.5 ;)  ) and does not "like" to eat- 

Our endo has had us talk to a nutritionist to "teach" us how to add calories to what he will eat-  you might want to see if this is an option for you (my boys see an endo at a large children’s hospital w/ onsite nutritionists). 

One of the things that seems to work for us is to try and make meal time fun-  I have gone as far as making a funny face on his waffle with whip cream and m&m’s- I know not the healthiest, but for a long time I was in desperation mode-  meal times would bring me to tears-  it is so hard-  One of the things that was suggested to us was to add the instant breakfast mix (the powder stuff) to my son’s milk-  it adds another 120 calories, also I was told milkshakes (+ the breakfast powder and a 1T of peanut butter).  I started to limit Tommy’s liquid intake before he ate too..........  he would rather drink all of his calories than eat.....  so I wouldn’t let him have his favorite, milk, until he ate some.  Now I let him eat at his own pace-  I gave up on the force feeding- it was too stressful for all of us, and he has come around some-  I won’t lie, some days are better than others and it is hard to let go...

sorry to be so long winded.....  just a "subject" that really hits home. 

oh and one last idea-  adding olive oil to every meal!  I think one table spoon is 100 cal.