D.B.
Make sure he can breathe through his nose while he's nursing. Once when my daughter was real small, she had a stuffy nose that got worse when laid down so I had to change her position so she was upright. If it is a stuffy nose, try to irrigate it out with some saline and bulb thingy.
8 months isn't a weaning age, babies still need breastmilk/formula until at least a year old.
You might also see if he will nurse when he's sleeping. Often its the easy way to "break" a strike, but usually when baby's been scared off the breast.