My son did a similar thing. He was a great day sleeper and would sleep virtually all day but night time was bad. He was awake almost all night. Not crying but not happy. he just had his days and nights mixed up.

Where does he sleep for his day naps? Jacob was sleeping wherever he fell asleep but I found once I put him in his cot for day naps he slept a bit better at night. I also found the more we got out and did things during the day he slept better that night as well