Worried We Are Being Deceived

I would like to know if there is anybody that wonders the same thing as myself.
I love the thought that one day we will see our loved ones again and that they can speak to us through mediums etc.
But there is one question that constsntly niggles away at me. It is "What if what we are told about the afterlife and the messages we receive from our loved oned through mediums is all a deception of Satan and his demons".
I have seen it asked befpre but the answers dont remove the doubt from my mind.
One answer was "But why would demons bring such words of comfort to us if they were deceiving us". Well that is exactly what they would do to us, they are out to lie and deceive us and to take us away from God.
Another answer was "Why would they do this, what can they gain from it". Their gain is to take as many with Satan and themselves as they possibly can and maybe people could end up in hell.
I dont mean to offend anybody with this question as it is a genuine fear and doubt I have.