Joeve, my Mum had some success feeding ebm by spoon with a couple of the little ones who weren't keen on bottles (temporarily or ongoing).

I was able to have DS with me or brought to me when he was that little. DD was older, and she would just hang out until she could feed from the breast, nothing worked for her. 15 weeks is a bit little to just wait til she folds though.

RhiChiChi, maybe the exclusive expressing women can help you with how much you would need. Is there a reason you want to switch from breastfeeding to bottle/cup feeding?