One thing which I've learned over time is that there is a lot of breadth in Christianity. Some denominations (and some individual Christians) make you feel that if you don't believe in a whole long checklist of things then you aren't a Christian.
But there are others, and lots of them, who acknowledge that Christ didn't give a lot of rules about exactly what you had to do, or a lot of doctrine about what you have to believe, in order to follow him. And to them, the idea of whether or not there is an afterlife is one of the many grey areas about faith.
The Bible tells us that there will be a new creation after this one ends, and that if we are in a relationship with God when we die then we'll get the chance to be part of it. But it doesn't say much about what that will be like, and the early church was expecting it to happen any moment, not after thousands of years. So how much should we assume they had anything more than a vague idea to go on?
I think as long as you try to follow Christ, and be true to his teachings, then calling yourself a Christian is ok. But OTOH you don't really need to call yourself anything to be yourself and have a relationship with God, so if you don't feel the label is right for you, then don't use it for a while and see how that feels.
Another things you could do, if you're interested, is try putting your beliefs into the Belief-O-Matic and see what it says about matches - I think you'll find it says that a belief in an afterlife is not incompatible with mainstream Christianity, but you might also find there are other denominations, or other religions, which are a better description of what you do believe.