I am so sorry you are going through this. It's a natural feeling, but such a painful one...and one that no one can take away from you. I ache for you, as I haven't fully grieved over the death of my father (will be 2 years on March 2nd).
It's true you can talk to your mom anytime, anywhere....but it's not the same. It's not what we want. We want them to BE HERE WITH US PHYSICALLY.
I want my dad's big bear hugs so desperately sometimes....
Just know that you're not alone....and grieving is a normal and healthy process, but indeed it is extremely painful.