How the Hell can I call myself a Christian?

I don't go to church, and I barely even pray anymore.  I have no idea if anybody (who doesn't know me) would recognise me as a Christian, even though I wear a Crucifix - because it is often just a fashion statement these days.  My biggest fear is that when I do die, I will be one of the people who Jesus was talking about in Matthew 7:21-23.

21 “Not everyone who says to me, ‘Lord, Lord,’ will enter the kingdom of heaven, but only the one who does the will of my Father who is in heaven.
22 Many will say to me on that day, ‘Lord, Lord, did we not prophesy in your name and in your name drive out demons and in your name perform many miracles?’
23 Then I will tell them plainly, ‘I never knew you. Away from me, you evildoers!’

But I do call myself a Christian.  Of course it all comes down to belief (specifically faith verses works, which is a huge debate in itself), but I do believe that Jesus is Lord.  Whether I am in a close relationship with God or not, doesn't alter the fact that God exists and Jesus is His Son who died for me. 

I've been on various Christian messageboards and forums (incidentally, I do think you can 'do' church online, because 'church' is the collection of believers and not some cold, run down building that you feel obliged to frequent on a Sunday), and have debated and been involved in various apologetics.  I do still find apologetics interesting, but don't have much time to spend on it these days.  What confuses me the most (and I truly do not understand) is people who claim that they were bible-believing Christians.  Perhaps they even spoke in tongues or displayed other 'signs of the Spirit'.  However, they came to their senses and now believe that there is no God, they were brainwashed, and no longer accept any of it.  If I only use my intellect (I've a Masters from Oxford - often I'm the more 'intelligient' one anyway) I would see as they do, and realise the 'truth'.  I honestly do not know how this can happen, if people did genuinely have a relationship with God.  As I said before, even if I say a million times that God doesn't exist, that doesn't stop Him from existing, nor me from knowing that He is there!

So, that is why I call myself a Christian.  I may not be a very good one, but I call myself one, nonetheless.