I have been sleeping at 3-4am for the past 1 month. Coffee doesn't affect me much. I used to drink coffee before bed time and I slept like a baby. But I'm beginning to think it is the culprit now :(
It's been the same for me. As we get older caffeine seems to be more prone to absorb into our bodies we metabolize both food and liquids slower. I no longer drink coffee anytime after noon or I too would be awake until 3-4am.
I don't have any caffeine past noon and I still have sleep problems. Dr gave me some medicine that works but I don't like using it because it seems to hold on so long. I'm sleepwalking through most of the following day.