strangly empty pool

I keep doing this thing where I wake up 4-5 times a night and check the clock to realise it is to early to get up - I'm not really sure why I keep doing this I know I need the sleep and I'm not stressed about my workouts. Last night I was super tired but I still woke up at 1, 3, 4 then finally got out of bed at 5:10 or so. I wish I would knock this off and just sleep till my alarm goes off.
So I got to the pool around 5:30ish to swim an easy 2500 yrds. There was no one in the lap pool - it was just weird - though I had my own lane for my entire swim which is always a treat. I did 400 warm up (300 w/ pull buoy), 50 x 2, 100 x 2, 150 x 2, 200 x 2, 250 x 2, 300 x 2. I actually felt pretty good, not super tired or anything. Though my muscles did not agree with that at all - my shoulders are tight and slow, my legs did not even want to push off from the wall, and my core is generally tired and a bit sore. I did not push things to hard and just aimed for good form and about 2 min 100s - since I was not really pushing myself I was able to easily keep my rests at 15 seconds between all sets. I did flip turns every other sets - I'm getting better but still a little slow and my abs complained everytime I did one. My shoulder got kind of tight/tired about half way which did not surprise me much since it was sort of tight before I even started. I'm not really sure what the shoulder issue is but sometime soon I would like to get it resolved since it seems to effect both my swimming and biking.