i am also trying to use a cup that doesn't have a valve and sometimes he sips it but other times he just spits it out. i don't think he is on a nursing strike but is just more distracted and maybe not hungry? he arches his back ALOT when i try to feed him and i considered relfux as he still spits up every now and then but don't think that is it anymore. he just went in for his 6 month checkup and there's no ear infection. maybe he just isn't interested in eating?? i've tried turning the tv off or going to a quiet room to nurse but lately he just won't have it. my milk lets down ok, in fact right when it comes out he decides to pull off and it squirts everywhere! argh...anyways, thank you for your advice and support!