I often think and cry about my grandparents who are now pasted, when I do, I feel a warm pressure on my back, like a hug, is this them? With me, letting me know that they are always here? My mother has had readings done with a medium, where she has "communicated" with them both in particular my Nan, and had things said that only they would know and things like an itchy head that Nan said was her! Is this for real? Is there life after death and are we still with our loved ones when they need us?

Yes there is life after death and it sounds like they are watching over you.