I can understand how you feel. I feel the same way. I even said to my husband before he died that I wanted to come with him and he told me I had to go on for him and our family - that my time would come when it was my time. It doesn't help the feelings of lonliness and despair and the what if's. I have plenty of those.
My husband was only 57. His mother is still alive and is 87 this month. She is taking it hard and has dementia and sometimes forgets he has passed on and tells me he took her to the doctor etc. when it was really his older brother who took her there.
We had gone through a lot of trauma the last few years with drought on our farm and selling it just over 12 months ago to retire and "enjoy" life and now I am alone to try to enjoy my life. He went through so much and now can't reap the benefits of finally being rid of the farm that was dragging us down.
If makes you wonder what life is all about and why it can be so cruel but we have to move forward as hard as it can be. My Mum died from multiple myeloma 4 years ago and my cousin died a week ago from myeloid leukaemia. It is a harsh world we live in but we have to find strength to carry on as hard as it seems.
That stairway to heaven will open for you when it is your time. I wish I could be with my husband but I know he is with me in spirit and that helps.