Hello and welcome to the forum. Thank you for telling us about your mom and please accept my sincere condolences. I remember when my mom died. She was in the UK and I was in Australia so I did not have a chance to say goodbye. I received a phone call from my sister telling me the news on Christmas Day.
For at least a year I came home and cried every night. Often I cried at work, disappearing into the toilets to have a little weep. There is no need to pretend you are OK. Everyone grieves for parents and other family members when they pass away. It's because we are human and not Superman (or woman). Grief also takes its own time to get over the loss. And it is such a huge loss.
I know we need to get on with our lives and carry on with our jobs. It is expected but do not let this be the only face you show. It's OK to be sad. Feeling lost and alone is part of the process towards healing. My mom died 20 years and I still miss her. Not with the overwhelming loss it once was but I still find I want to talk to her at times. So I do. Not in public because it would not be understood, but in my own home.
Does your employer have a Employee Assistance Program? If so it may be worthwhile to have a chat to one of the counselors. You can cry and get upset in that very safe environment as you work to heal. If there is no EAP perhaps you can ask your GP to refer you to someone about your grief. It doesn't mean you will forget mom or stop hurting immediately. It does mean you will have a safe outlet with someone who understands grief and loss.
Posting on the forums may also be helpful. I think most of us have suffered a huge loss of some sort and understand the pain this brings. No matter if the death was expected or not it is always a shock when it happens. We humans are good at hiding stuff from ourselves.
Don't worry about the housework. It will get done when you are ready. Have you considered asking your GP for some help to sleep? I don't know what your attitude is to taking meds but I make the suggestion because you do need some rest. I suspect some of your confusion is due to sleep loss. Remembering your last sight of mom is hard. When this happens can you substitute a picture of mom doing something she loved? At least until the rawness of your loss has calmed down a little. You will get through this time.