This is a post i had made on this thread It sounds like the same sort of thing and possibly the same solution, hope this helps.
I experienced the exact same thing as you when dd1 was around 13 weeks. Only i had been supplementing using a bottle as i had Mastitis 4 times which had majorly decreased my milk supply. The rejections was so bad that my dd would not allow me to hold her in the cradle position even when we were fully clothed. She would scream until she was loosing her breath.
What i did was ditched the bottles COMPLETELY. i would feed her using a large feeding syringe (free from chemist) and also the Medela Softcup Advanced Feeder, this meant that i was not spilling any of my "liquid gold" whilst trying to get it into her. Also, her sucking needs were not satisfied and usually when she was really tired or actually sleeping i could get her to latch onto me using a nipple shield - as she was used to the texture of the bottles.
Then i started a mission to get dd to associate my breasts with a "Happy Feeling". The way i done this was by laying dd on the floor and blowing raspberries on her tummy until she laughed, then i gently and quickly touched her face with my bare breast. We done this nearly every waken hour throughout the day for about 10 days then she started to show loving signs of the breast again. She would happily cuddle into my breast and would let me hold her happily whilst i was clothed or not. Then suddenly whilst playing "Happy Breast Time!" she quickly rooted and latched on - i was on all fours on top of her but managed to stay there until she was finished! I honestly felt like opening the house windows and screaming to let the world know how excited i was.. this was around 2 weeks after we started it. Then we spent about a further week around the house.. sleeping together naked, bathing together and playing together naked! If you have a sling carry your LO in this whilst going out rather than using a pushchair.
Before long we were back in full swing and the bottles were long in the bin.. we managed to continue BFing until she was just over 2 and she self weaned as i got pregnant again.
You Will get through this.. Just remember even though you are feeling that he is "rejecting" you, you are the person he loves most. It is just a case of pchycologilly training him that the breast is for happiness.