Hi L.. I went through the same thing when my daughter was 9 months old. My daughter's refusal to nurse came out of nowhere, lasted a few days, and just went away almost as quickly as it came. She would cry and arch her back and turn away from me when I tried to nurse her. I don't know what caused it. I also thought that she was ready to wean and felt saddened by it because I wasn't ready. Turns out she was just on a strike because she will be one year old on Wednesday, and we are still going strong! :0)
If you are willing to continue breastfeeding, I wouldn't stop. Your son probably isn't trying to wean. He may just be on a strike like my daughter was. I think as they grow and develop and learn to do things like crawl, stand, and walk, they would rather do those things than be still and nurse. Kind of like how they start to hate diaper changes because it takes too much time out of their day when they could be doing something else. :0)
Keep offering him the breast and really try not to put the milk in a cup. It's okay if he misses a feeding every now and then. If you can, maybe even try to spend the day with him while you are topless and let him nurse whenever the fancy strikes him. This seems kind of odd, but I found out (by accident) that if I am holding my daughter while I am topless she often starts to nurse (even it's just for a few seconds or minutes).
Good luck, and hang in there!
J.