Is it okay to use more than one type of bottle? Will baby get confused or have a hard time going back and forth between breast and different bottles? We registered for the nanobebe set and were given a few nanobebe single bottles as well but I’m wondering if it’s okay to also get some of the Dr. Brown’s glass bottles/other glass bottles for the convenience of diaper bag pockets and cup holders as we travel frequently. I plan to exclusively breastfeed and pump.