loosing my lovely dad

my Dad died on 1/12/20, although it was expected it all felt very sudden. My dad had suffered with cancer since I was about 11 but I was always used to watching him go through chemo and then get better again.
Due to him being vulnerable to covid he moved out in march so we could shield him. this meant he missed my 16th birthday (which I didn’t know would be my last birthday with him around) and just missed out on time we could have spent together. In September dad started rapidly declining which was so tough to watch as looking at him I could no longer see my dad (which I feel so guilty saying)
He passed away in the evening on the 1st of December with us all by his side.
I just feel so angry I didn’t get enough time with him and that my mum and sister got more time and memories with him- which is selfish I know. My dad was truly my best friend and im finding it difficult to even come to terms with the fact I won’t get him for the rest of my life. Recently I have began to feel like I never had him at all. Him being here, healthy and happy feels like such a distant memory and I can’t picture even just sitting with him anymore and its only been just over a month.
im scared that I will eventually forget him and his presence completely.
I don’t know if anyone has any advice in how to cope and keep the memory of him alive in my head.