Hello Sal23, and just to say, so sorry for your loss.  I experienced the same thing when my Mum died many years ago.  In fact, it took me about 16 years to actually cry for her.  Grief is very strange.  I knew a Man who took 20 years to fully grieve and cry over the loss of his baby sister.  You might find that grief counselling could help you.  Your Doctor would be able to advise you on this.  Your Mum passed  only 18 months ago, and it is possible that you are still numb from the shock of it.  My thoughts and prayers are with you, and I wish I could offer more words of comfort, but I can only say that I understand what you are going through, take care, xx