You need to get help.
You need to. Now. Before DS grows up thinking that no matter what he said and did, he was not enough.
I feel terrible saying that to you. I don't want to kick you when you're down. But it is the truth.
Yes, it appears you are unlucky at having babies. I'm sorry. But that means that only in that instance are you more unlucky than others. There are women in poor countries having baby after baby...to watch them die of diarrhea or malnutrition. There are women who have babies...and husbands who cheat on and abuse them. Just recently someone near-ish to me was pregnant with her fifth child, quite far along. She was stung by a bee and had a freak allergic reaction. She died. So did the baby, obviously. So there her husband is, mourning his wife and daughter and four kids under the age of seven, all looking to him. Do you honestly think you are more unlucky than they are?
And Christmas doesn't have to be a build up to just one day. It can be lots of little things...a special DVD with hot cocoa a few weeks before. Decorate some cookies (you can buy it all if baking seems too much). Special Christmas PJs. Write a letter to Santa. Read a special book. Take a drive and see the lights. Just little things here and there.
You posted before about seeing your pictures of your DS as a baby and toddler and feeling pain. If you don't get help, you are going to let that happen again. When he is a big ten year old, you will look back on a picture of him at five and think "oh he was so little!" He still is very little, and you are letting this time slip through your fingers.
You think he'd be better off in a "proper" family? Well, you and DH are the only parents and family he will have. You are the only mother he will ever have. If what you say is true, this is the one chance you have to be a mother, and you are letting it go.
I know you don't believe me, because you believe the depression. But depression lies.