One of the things that occurred to me after my brother's death was how many other people have gone through a loss. How life goes on, and it's a blessing and a curse. Sometimes you can't understand how the world can keep turning without that person in it, and sometimes you need to know that everything keeps going and it'll all be okay.
The best advice I have to offer is to know that no matter what you are feeling, it is the right thing for you to be feeling. There's no such thing as "getting over it" but there's no timeline and no checklist for how to grieve. Take care of yourself the way your mom would want you to, and do the things you need to do for yourself and your family.