Oh no Sheree! What do you think the problem is? We narrowed ours down to a slow bowel and if it had been a few days since she had done a poo then she would refuse. Still can't explain why she would refuse the breast and not a bottle though. It sorted itself out by 6wks. You don't think AF is coming do you? That can put them off...teeth are a possibility too as they can show teething signs up to 4mths before they actually get any teeth.
Oh I hope Riley sorts himself out soon, he has been such a good boy! I'm sure I've heard around the 6wk mark they get a bit fussy...they go through a growth spurt at 12wks (or thereabouts) so it could just be that, whatever it is I hope you guys get through it soon