Welcome to the forum. Please accept my best wishes and condolences on the death of your mom.
When my mom died I felt pretty much as you do. My dad had died a few years earlier. Like you I kept expecting one or other would come walking down the road to see me. I would run to the window to wait for them only to realise (again and again) they were not there and had gone forever. I know how I felt and I think you are remembering and feeling in much the same way. I'm not sure which was the worst, the fact they had died or they were not coming to see me. Doesn't really matter because both were so dreadful.
My heart goes out to you at this time. I cannot take away your pain but I can offer to walk with you for as long as you wish. May I say, even though you will not believe it now, that you will heal. It will take time unfortunately as such grief runs deep and takes time to feel better. You will never forget her but the times between remembering will get longer.
Do you live on your own now? If so is it possible to live with someone else for a while. A family member or close friend. Perhaps someone can come and stay with you for periods of time such as weekends. It will help to have someone around, someone who knows how you feel, (as much as anyone knows how another person feels), someone who cares for you.
Although it was only mom and you living together do you have any extended family? If so I wonder if you can arrange a bit of a family gathering to rejoice in her life, to reminisce, to remind you of family jokes etc. Bring out the photo album and talk about the good times. If you are living in the house and own it, perhaps you plant a tree or bush in her memory. Some people find this helpful.
It probably sounds a bit weird to do this but it can help. Holding a memorable of sorts does bring comfort. You can express your feelings and be comforted by those who care about you.
We both know this grief will take a while to become bearable. Talk about mom when you wish and be angry this has happened, want to bargain, shock, denial, depression, testing, and acceptance. This is normal.