Baby wont eat

I need some help ladies. I have been babysitting my nephew for almost 2 months. We started when he was 3 1/2 months. He was exclusively breastfed when he started coming over. She had tried giving him the bottle here and there but he barely took it, and when he ate it was very. The first 3 days I had him, and I tried giving him the bottle he WOULD NOT EAT. She comes over on her lunch break to feed him and that would be the only time in a 9 hour period that he would eat. We've tried multiple bottles, temperatures, positions, I've used things that smell like her, I've gone to rooms she's never been in. He would not take it. Out of desperation and a need for him to eat, I started spoon feeding him breastmilk. I would still try the bottle before during and after, but he wouldn't suck on it and would usually just start screaming when it touched his mouth. This week I decided to try another bottle with a faster nipple, that way if anything it could drip into his mouth, but he could get used to the nipple feel. He did great for the first 2 days and now he's getting pissed as soon as it comes near his face. He also wont take pacifiers just fyi. Sooo...does anyone have any tips on how to get this kid to take a bottle? Please help. Sorry so long.