Feeling rubbish and guilty

My dad passed away nearly 2 years ago, but for some reason it is hitting me again today. I feel so guilty that I didn't sit by his side while he was passing. I was thinking of going back to the hospital on my own later, but it was too late. It was 4-5 days from when he went into hospital, seeming himself apart from stomach pains and within 2 days the difference in him was shocking. Having been having chemo for bowel cancer and it being quite successful, he then developed a complication and had peritonitis and had burst and so was poisoned by the fluid, I think due to him falling in the middle of the night as he was unsteady on his feet. The last day we saw him, he looked so bad, I couldn't face remembering him like that and my mother and brother was with me. My brother couldn't stay at all and my mum broke down and didn't want to stay either. I think maybe if I had been on my own I would have stayed by his side - and that keeps haunting me the "what ifs". I don't think my dad would have wanted us to see him like that, but I can't stop feeling guilty leaving him alone. He was the kindest, best dad ever and I miss him and his jokes