I'd def spk to a MW..i've had someone out many times to help me. BF counsellors were great.
Yes..you can mix BM and FM...i've done it for the last 4 months. I don't express much off at work but add it to the FF for carers as its better than nothing. Just add BM when you need bottle straight away. I wouldn't advise adding already stored cooled BM to hot formula and then leaving in fridge until later.
Hope that makes sense as it would mean you'd be heating BM and cooling again and then heating up later.
Sorry, waffling, baby brain still present :) x