What can cause a person to forget a segment of time while still being conscious?

I keep forgetting segments of time within my daily activities. For example; I was laying in bed, texting my girlfriend and the next thing I know, I'm standing in the middle of the bathroom naked and wet. Obviously I had taken a shower but I have no recollection of the event. Another time I was outside and then suddenly I was laying on my side on the bedroom floor. I have to be functioning normally during these blackouts but I can't remember a thing that happened. Later on, I noticed a bump on my head but I don't remember hitting my head on anything. A day later I noticed bruises on my shoulder, hand and foot and I have no idea where they came from.