Be patient Becca - big conversions can take hours
Whilst you're waiting you could try converting the PDF to PRC using MobiCreator - my experience is that its quick, the output file is usually much smaller than PDF->Word
Converting PRC to MOBI is usually very fast as they're essentially the same thing, see
https://www.mobileread.com/forums/sho...nce+.mobi+.prc
BR