Me an girlfriend broke we don't speak but we have a son together.she walked out please help I miss ny son

You need to define what you need help with. If your girlfriend is preventing you from seeing your child, then this is a legal issue and you need go to court for custody/visitation. Also this would need to be moved to the Family Law forum.

What is the issue with your ex and yourself? I doubt it is highly as simple as 'she just walked out'. You need to do your best to resolve the issue between the two of you for the sake of your son.

Dragging her to family court before first exploring all of your options with her is probably not in your best bet. Family court is likely to award you once a week, or once every other week visitation (in normal situations) and if you were to try to resolve the issues with her you and her may be able to come to more suitable arrangements, with more visitation for yourself.

You and her never had to say another word to each other if you don't want to.

File for some level of custody in court, get at least visits. Arrange for it to be done in a public place if needed, police or fire station are often used if there are problems.
Arrange to pay child support and start seeing your child

Many times trying to settle issues like these get more complicated when you try it on your own. Not only that , if you seem to reach an agreement , even in writing, it essentially means nothing and cannot be enforced.

Pay your support. Get a lawyer and have your visitation or joint custody court ordered. Then there is no question and you will be seeing your son.
And I can tell you from experience that any financial hardship getting a lawyer and getting this done might cause, is worth it. I sold a new car and got "basic transportation" to get the best attorney I knew of. Among other changes in lifestyle.
No regrets. Happy I did it.

I agree with others here do this the correct way, via a solicitor or lawyer/attorney, take it to court and you'll be granted visitations, and of course you will also have to pay child support, for your child.