Hot and cold parenting..

I really am not sure where to start but here goes,
I have 3 children, the youngest one has a different dad to my older 2. He was a fling, meant very little and we were using protection but still ended up with bub. From the beginning Bubs dad has been in and out, I wouldn't hear from him for months at a time during my pregnancy, then he would want to be involved with everything, then suddenly nothing for another long period of time.
Despite this I agreed to him being at the birth, but since baby has been here there have been a number of long periods (5-6 weeks) of not hearing from him and even longer periods of not seeing our child. I don't want this for my child, a dad should be in or out not all over the place. My child has no idea who he is and screams whenever he is near. Do I continue to put my child through this? It's still only early(ish) days.. Or do I cut him out completely? I don't want my child being put through hot and cold parenting. All or nothing when it comes to being a parent, but I have always been against being the person to exclude my children from their dad. He has another child whom he dotes on and sees on a weekly basis but sometimes it seems he just can't be bothered with this child.. No one can answer I know this but I feel for my child, and at a loss of what I need to do!