Hey there,
Izzy has trouble getting burps up so i have to try lots of different positions like lying her down and then sitting her up to use gravity, sitting her on my knee with a hand under her chin and rubbing her back, picking her up under the arms and kind of letting her hang!! for a bit, over the shoulder rubbing her back, and sitting her with her back on my tummy and rocking her withmy body back and forward.

I also do cycling exercise with her legs while shes lying flat on a sheep skin and bend one leg in to her tummy with the other stretched out! Some of these work occasionally!

Ive been told onion, cabbage, chocoalte and caffeine are no nos, but really it could be anything so an elimination diet might be the go.

Also Ive bought Brauers colic relief and I give that to her 2-3 times a day and it has really helped too and its all natural.

Isabelle is very sucky too so i give her a dummy at those times that she just wants a nipple for 2 seconds to fall asleep!
HtH!! and good luck!!!