Does he go for long hours to daycare he does sound as if itsconnected with being ther, do they give him enough attention, sometimes Daycares are so overloaded, how does he spend his day , does he have games and does some play with him, read to him take him out? if you can afford to do it cut back on daycare,and make sure he has plenty to do.
It sounds like he is stressed over going to daycare..