my baby boy is also 13 weeks and sleeps heaps (i just count myself lucky)
sam wakes at about 8am has a bottle back asleep by 9am wakes for next feed at 11 or 12 back asleep by 1.30 wakes for next feed at about 4pm sometimes stays awake for an hour or 2 back to sleep till 7pm has another bottle and a little chat back in bed by 8.30 and i dont hear from him till 8am the next day .He is a smiley bub and loves a chat he just likes his sleep ,dont worry just think once he starts teething you will be wishing these days back lol.