Oh my goodness, poor you. That is all just so sad. I can only share my experience and hope it might help...
My 91-year-old grandmother died in October, and then my little 13-month-old daughter died totally unexpectedly three days later. I actually haven't really registered my grandmother's death, as she was old, but I have been consumed with the searing pain of the loss of my beautiful girl. Before Christmas, I was feeling absolutely desperate, as if the grief was totally new again, as I was alone in the house for the first time. I felt that I was never going to emerge from this well of sadness and tears. Like you, I thought I would never feel better again.
Fortunately, DH and I had forced ourselves to take a holiday and we escaped Christmas and New Year. And to my surprise, the trip turned into a holiday. We even enjoyed ourselves. Sure, there were tears, but also smiles. The time away, by ourselves, meant that I didn't have to be the focus of others' grief and concern and expectations, and face questions of 'how ARE you?' At the same time, I could cry whenever I wanted, or smile whenever I wanted, and not feel that I was been assessed every second. It has really helped. I feared the entry to the new year, but it was very gentle, and I have been able to come back home with a little more energy in my step, and a little more ability to think about the future again. There are still sad times, and downs, but that is now part of my life.
For me , a holiday break was really helpful. Writing on here about my daughter has helped enormously too.
So yes, I can promise you that you will feel better one day. But there is no formula or special pill or timeframe. And you will still have bad days. I think that it will be difficult to put the sad losses behind you, but perhaps you can accept this as part of your life, if you can. Here are some words my aunt wrote to me, and I'd like to share them with you, if they help :-
Give your self time. Not to get over this loss because you will always grieve but to somehow weave their beauty, their love, your love and your terrible loss into a fabric that can be worn as a shawl of love.