I don't think it has anything to do with his day care situation. Babies won't go hungry, and he doesn't have the comprehension level to understand the difference yet.
He's at a critical stage in his development - he's likely going through a huge amount of change, getting ready to sit-up on his own, requiring less sleep during the day.
When you nurse him, do you do it in bed on your side so you can sleep while he's nursing? I, too, worked full-time while nursing our son (different story with our daughter, but not relevant for this conversation). I was driving up to 200 miles/day, and I needed the sleep desperately. It was a life saver.
Ask your pediatrician about cereal before starting. Both of our kids started at 4 months upon ped's advice. Not all peds have the same philosophy.
He may also be teething, have an ear infection, something he can't tell you about that is waking him and is being soothed only by nursing. Our 2 year-old has had tubes twice, the first time at 10.5 months. Her only symptom has been horrible drainage from her nose. Otherwise, we'd never had taken her to the doctor.
Good luck - be patient. The sacrifice with an infant is toughest on you, but it's worth it.