HELP 6 mo old won't take bottle!

My son is breastfeed by nursing and by bottles. Within the last few weeks he has taken less and less bottles. Now he will only take one when I've been gone to work for hours and he only eats just enough to get by. He has started eating baby food. I've tried sippy cups and different types of bottles. I'm so worried that he is replacing the milk with food. He nurses a lot when I come home like he is starving. I found out my mil has been giving him watered down juice since he won't take his bottle which has me extremely upset. I'm just hoping I can get him back on track with his milk. Any advice? 😞