I'm having a hard time believing that I'm still not over jack dying
Grieving can take a long time. Why do you think you're not able to get past Jack dying?
There is no other reasons and I feel like I still can't get over it
Letting go of someone that died doesn't mean you forget the past or suppress memories of your loved one. Focus on the good times with them and try to honor their memory by living life to its fullest.
I'm planning on forcing myself to forget about him.
It's important to move on after the death of a loved one, but you really don't need to forget them. It's good to remember people we've lost. Eventually you'll even be able to enjoy talking about them with others.