your chances of 50/50 are slim to none get used to one night during teh week and every other weekend. where your going is a womans world. and don't pay till your ordered by the court. i knew someone who paid for nearly 4 years with reciepts then his ex took him to court and he had to pay from the day the baby was born the court considered the 4 years of payments as a "gift".
But you can buy things that are necessary like food, diapers, formula, clothes. just don't give her any cash till you have to.
actually the best way I've seen to deal with this is to set aside what your presume the child support will be into a savings account thats at the ready to be withdrawn for if they backdate
very rarely does a court go back to birth...but they will go back to the date the motion was filed
my husband got nailed to pay back his ex-skanks fricken welfare though...that was a fun bill