First of all, please do not open duplicate threads. Take this as the last warning before you get banned from the forum.

Coming to your question, you can submit proof of supporting your child since you went to Pakistan by presenting the bank statements but for the money you have been paying in UK, the letter your girl-friend wrote is not sufficient as far as I can guess. In any case, you will need to consult a qualified solicitor who can give you advise specific to your case.

And yes, you have already abused the immigration system by overstaying which is a crime and just because you went back to Pakistan on your own, doesn't mean you have washed it off. Also, ECOs are smarter than you think and will find out that you are trying to decieve them. That will most certainly bring a ban of 10 years on your entry to UK.