The eponymous title of this thread describes my coffee habit. I take it black if it's a quality medium roast. I don't drink decaf.
I usually drink 3-4 cups after supper and have no problem sleeping. Caffeine doesn't really affect me.
It's most likely that you have built up an addiction to the caffeine to a level that without it, you'd be dysfunctional until your system re-balanced.
I can drink coffee up to going to bed. Can't sleep with it, can't sleep without it. Can't sleep.