So sorry to hear of the loss of your Mum, you remind me, how much grief my daughter had and still has when my wife passed away also very suddenly after 49yrs of marriage 5mths ago also to cancer. Daughters seem to grieve much more for their Mums than sons do, thats only based on my own experience of course, and I have noticed that it's rare we see posts from sons who are grieving for their Mum on here.
Daughters tend to be much closer to their Mum, and as a father who is also grieving we sometimes overlook how it affects the family especially the daughter. The symptoms you describe are well known to us on here, as we have all had those symptoms, when you lose someone you love so much and then they are gone, it's natural they leave a big emptiness in our lives, and we even wonder how we can go on living without them. My sons grieving ceased at their Mums funeral so they tell me, and 5mth later in the rare event I see them they never mention her, it's as though she never existed.
Yet my daughter who is 40, speaks about her Mum every day when she phones me, indeed I think if it were not for her support I doubt I would be here today, I suppose we gave each other support as I've replaced her mum on the phone as rarely a day passed when they didn't phone each other.
You need to take it a day at a time... the inner emotional pain you are feeling right now will decrease with time, and it will take time, I still cry like a baby some days, and I'm 71, indeed yesterday was a very bad day for me, but those sort of days will become less frequent, it will take a long time, but eventually you will be able to remember the great times and fond memories of your Mum without shedding tears and getting that indescribable painful feeling inside. It may be worth having a chat with your doctor too, just to be on safe side, it certainly won't do any harm.
Remember....A day at a time....you take care.