Is it me or the ex wife

My husband and I coparent with his ex wife. I find myself constantly comparing myself to her. My first marriage was horrible and ruined my self esteem so I know this is partially the reason. My current husband told me from the get go that he will always love his ex bc she is the mother of his children. I feel like that is another reason for my self esteem issues as I have absolutely no love for my ex husband even though we have a child together. So do I get it together and move past this or move on?

My advice would be "to not worry about something, until there is a reason to worry". If there isn't really any cause for concern, then all you are doing is bringing unnecessary stress upon yourself. As long as he doesn't behave inappropriately towards his ex, there is no reason to be concerned.