refuses breast

Amber
😕 little man is 5months old and lately he only will feed from the breast if I'm "full", like in the morning. Otherwise he fusses and fights til I give him a bottle of expressed milk. 
It started with him just doing this on my slacker boob side... and now it's both unless it's been a while! He is very used to a bottle because he's in daycare but it hasn't been an issue at all until about 1-2 weeks ago. 
I know it's easier to eat from the bottle and the breast makes him work harder... but any tips or suggestions? He's on a slow flow nipple on the bottle and we pace feed