Please don't feel badly for venting or for expressing yourself. There's nothing wrong with that.
I'm sorry I don't have any magic words to make this easier for you. The idea of an afterlife is, from what I understand, one of the hardest things to let go of during a transition in belief. It's a lot to get used to.
Do you have a Unitarian Universalist church near you? If so, I'd really recommend giving it a try. UU had it's start in Christianity, but (loose description, as not every UU church and believer shares a belief system) it's more about the personal journey towards a truth, not so much about customs and set beliefs. Everyone is accepted there - more than 3/4 of their membership
isn't Christian. It's a good place to go if you feel the need for fellowship or a sympathetic ear.
This journey is a tough one, but you are not alone.