If you need to cry, just cry and tell somebody that you are very sad. It's better for you to express your sorrow rather than suppress it. Your mom is just leaving temporarily and she is in the hand of GOD. you will see her one day...
I had similar experience 3 years ago. Up to now, I will cry whenever thinking of her. Accept your feelings and share with ur relatives, friends. You will see how God soothes you.