11 month old fussy eater

hi i totally need help, my 11 mnt old,,,is a fussy eater, he will only eat custard foods,,, and we have to get his weight up. I have taken him to a pediatrian just to see whats going on,,, well his bloods came back positive,,, with everything ok,,,and he still isnt gainin weight, ive tried finger foods, to smash food to dairy products, just to find if he had a particular food he will enjoy,,, he is still bfeeding, i totally need help cause my boy is such a happy go lucky kid,,, but he seems tiny for his age. We thought it may be the fathers side cause he is tiny and skinny,,,where as my 2 yr,, is short and chubby like me,,,and he had no problem with eating,,,i will be making an appoint to see my local health nurse to see what they can help me with, but if anyone out there that has some other great ideas,,, i will be totally greatful...

how many bf is he having a day? could he be filling up on milk?

This is just what I'd do....some wouldn't agree and might not suit.
I wouldn't give him custard foods, he could be only eating them as he knows if he doesn't eat other stuff then he'll get custard. What we do with DS is put stuff on his plate- enough that I'll know he'll eat, if he doesn't eat it I don't offer anything else, we do offer a range eg Lunch will be a few types of fruit, sandwich, rice cracker with some sort of topping, cheese.
He'll eat it if its hungry, if he throws it or doesn't eat it I keep it to one side and offer it at the next snack/meal time.

I have to aggree with nadz27 even though he's 11 month they are very smart to learn about how to get the food they want.
What i was going to ask is, is he a very active boy. My boy kind of didnt put on weight around this time as he was crawling alot and losing all the baby fat.