I also find the feeling of fullness to be highest first thing in the morning if I take PM right before bed. As a matter of fact, on mornings when I have taken PM at night (I don't have a regular schedule for it at all these days), if I wake early I feel that fullness more strongly. I am talking about taking it around 10PM and being awake at 3AM, instead of the usual 6AM. Since I'm fairly certain PM can't tell time, I suppose that suggests that during sleep, the body simply isn't making as much use of the hormone variants which are higher in the morning. My experience (and it sounds like I'm not alone) suggests that adding PM to that "recharge time" changes the balance of what is generated and what is used. It appears to change that balance in favour of breast development.

YMMV