My baby is 18 weeks and started refusing feeds at around 12 weeks also. I don't know why, but i found what works for us to get her to eat. I know she wanted to eat because she would scream hungry.
So first thing is that i swaddle her before feeding, this way her arms aren't constantly hitting the bottle.
Second is she has to be in her bed, in the dark room with minimum visual stimulation, also flat on her back.
Third, is she eats best if i feed her to sleep, ( i know thats not how its supposed to be done, but she takes 2x more milk that way), and surprisingly she is not dependent on a bottle to go to sleep, she would sleep without it if I put her down, as long as she is not hungry.
Also, the MOST important thing that helped her eat, is that I took away the pacifier. She used to suck on her pacifier, but refused the milk, and once it was gone, now she drinks everything that i offer her!! That is a huge change, as I was throwing away 2/3 of the milk i pumped.
This is just what worked for us.. Hope this helps