Refusing to eat on Right breast

Sunny

I'm in need of advice for anyone that's had their LO all of a sudden refuse to eat on one side. He's 11 weeks, been nursing great. Yesterday all of a sudden refused to eat on the right side. I've finally gottwn him to eat on th right by sitting him up but won't do it longer than 5 min. No fever, no booboos that I can find. Any ideas appreciated!