Is this parental alienation?

[Geri]

My ex and I split up when child was 1. Son is now almost 5.

He's an active Dad - 50/50 custody, pays support, insurance.

But he is not a good ex. He excludes me from everything. I think he wishes I would just disappear.

Ever since our split, I've wanted to do events (like son's birthday) together. And ex has said no.

Ex is now married, and I've seen on Facebook pictures of the three of them pictured together with Santa, at his birthday parties (they started dating when our son was 2), etc.

Recently I found out that our son (son told me) that he played on a soccer team and had swim lessons. I HAD NO IDEA! I looked at my ex's Facebook and saw a photo of his wife holding my son with his soccer medal. I was so upset.

As my son is getting older, I realize that he has nothing with us together - no pictures, no memories. I don't think our son sees us as a family - or ever will - and it makes me sad.

I recently asked my ex why he doesn't invite me, and he told me that we don't get along and he'd prefer to do things separate. He told me that he doesn't know why I am upset because he said he doesn't/wouldn't care if I didn't include him.

He told me to create my own traditions with our son, and to basically get a life.

When I brought up Santa and how upset I was about that, ex told me next year that I could take our son first.

As hard as I tried to explain, ex didn't understand that I was upset because I wanted to be there as a FAMILY. It's not about who takes him first.

I'm worried that my son will never see us as family. It will also be Daddy/stepmom there... and Mommy way over here.

Can I do anything in this situation? Is this parental alienation?
Merlin, I am not his father. I am his Mother.

As a Mother, I brought our son into this world and I feel like I should be included.