2 month old child and you have feeding issues and supplemented your milk with isomil. in your question i identify problems,
nipple issues
nipple confusion to your baby.
babies growth concerns and maternal anxity.
mam try to express your milk and give it by spoon after the child has finished a breast feeding session.do not use bottle as milk in bottle trickles down childs throat by gravity and whereas the child has to make an effort to extract milk from mothers breast.then check the childs growth on a growth chart if his graphs are showing good growth then alls well,then again isomil is a bitter formula better try nan -low lac instead
Next Steps
see lactational videos on you tube that should help