If she wants child support, take her to court and ask for back child support for the 5 years she was getting her life together. Now that she's on her feet, she can pay back the child support. You are also entitled for 50% custody and visitation. You can try and deal with her and tell her that you will pay for whatever your son needs directly but I doubt this will work.

Blackmail is a crime, don't make problems where there isn't any. As Betty suggested above, you could always ask for child support for the time that you were the sole caretaker if she tries to collect on you. But I would consult a lawyer before agreeing to anything.

Get back together and re-marry .

Get saved and then as a child of God you can trust your heavenly Father to take care of things even if you have to pay some child support.

Society, whether it's fair or not in your particular case, stacks alimony and child support in favor of women. The odds you will get out of child support are extremely small. Also the odds something as minor as genital herpes is going to hold sway over her are also very small. I don't think that card is worth playing.

My advice is look up the laws in your state and see for how long you might have to pay child support. The kid is 17. In some states as soon as they're 18 it's over. Most likely if your ex is as irresponsible as you say she really has no idea how the laws work. Just do some real homework and use that to your advantage.