You love him. In that case, it's time for a different plan. Time for you to face the reality that what you are doing isn't working to change him, his feelings or behavior.
The only thing you can do is to change you, your attitude and behavior. With that in mind, it's time to stop expecting him to change--right now. If there is any small amount of love and committment in him towards you and the marriage, then there is hope. But how you are approaching this has to change.
I wasn't kidding about shaking the sugar tree. He is taking you and love for granted. He thinks you will keep going with the status quo.
It's time for you to feel better about you, your home, your health, your work, your child. It's time for you to love yourself enough to stand tall, hold your head high and tell yourself something like, "Okay, you love the guy even if he is being thoughtless and knowingly being hurtful you. That doesn't mean you have to take it lying down, gal."
Instead of desperately chasing his affection, let him know by your actions that since he insists on paying his attention to others, you're going to back off and concentrate on you, your child and your life for a while. Still do the routine things for him that you are doing, but stop with any romantic gestures or over thoughtfulness towards him. Continue being thoughtful to you, your son, other people.
Makeover your life, including you. Improve things. Show a new confidence. Show him that you have a life outside of him. Go an extra mile with your appearance: for YOU and your child, not for him, though he will notice. Think about it, he notices you look great, new hairstyle, nicer skin, etc. but you aren't paying extra attention to him anymore because you've lost that aura of desperation.
If you are confident, smiling, holding your head high and look like you care about yourself, you're going to turn a few heads. Hopefully that will happen any time you and he are out and about. Maybe his friends will notice and say something to him about the changes in you and remark about it. That you look great and you look happier than you have in a long time.
Don't sit around waiting for him to pay attention to you and your child. Go out. Do things. Take a class. Go out with your friends one night a week. Join a bowling league. Learn to be genuinely happy on your own. Be busy if he suggests you go with him to do this or that. "Oops, honey, that's my girls night out. Next time, maybe?"
Concentrate on your family and extended family. Only do the dutiful things for him and his. But do it with a good, but more neutral attitude. "Yep, I'll take the casserole over to your mom's on my way to my ball room dancing class. I won't be able to stay, but I can drop it off. You understand."
This strategy will increasingly make you feel good about you and your life. It will be good for your child. If it doesn't change his behavior, then it doesn't. It's the best chance you've got though. And meanwhile, it's going to help YOU. Since he isn't going to help you, you need to help you.
Shake that sugar tree, girl. Confidence and self respect can be very alluring, even sexy. Do it most of all for you and your child though. Hopefully the side affect will be that he gets his head out of own selfishness and turns his attention back where it belongs.