I don't think there is much prospect of securing residence for your child in those circumstances. See this from the relevant UKBA web page:-
Children cannot normally come to settle in the UK unless both parents are settled here or have been given permission to settle here. The only exceptions are where:
1 parent is dead and the other is settled or coming to settle here; or
the parent who is settled or coming to settle in the UK has had sole responsibility for the child's upbringing or the child normally lives with that parent and not the other parent; or
1 parent is settled or coming to settle in the UK and there are serious reasons why the child must be allowed to come here.
This is the full page, in case you wish to research it further yourself:-
http://www.ukba.homeoffice.gov.uk/visas ... /children/
You don't yet have Indefinite Leave to Remain, and your brief resume suggests that you could not establish that you have had "sole responsibility" for the child.
Somebody may have some other suggestion, but I can't think of one myself.