A sleep deprived fog

My LO is almost 12 weeks and is occasionally sleeping all night. I say occasionally because it's only happened 3x and not in a row. Anyway, last night was one of those nights. My husband began his vacation yesterday and I asked him to try and put the LO down because I was so exhausted. He gave him a bottle and all was good until he finished it. The point is the last thing I remember was my hubby giving me the baby in bed to "top him off" because he was crying pretty heavy that had to be around midnight. I woke up around 3ish Bc I heard him cry, ran to the bathroom before I was going to change and nurse him I came back to him and he was sleeping so I went back to bed. Then the same thing happened at 5am. I went back to bed and woke at 7am totally confused. I feel as though I'm in a fog, what's going on? I'm pumping now at 7:30 Bc my lo has never gone this long without nursing and he's out cold. I'm so confused and tired. How could it be that he slept all night and I'm still exhausted! And what's with this crying a lil and going back to sleep? Nightmares? Idk I'm still exhausted and lil slept through the night, yikes. This happen to any of you? 

Have a lovely Sunday!