Why has he changed his mind???? pplease help?

i dnt want this t be too much info bt wud realli like help my boyfriend has a realli high drive n i neva have t ask for bt recently he has gne off it n last time we had he wasnt even fully erect whch he always has been n i have asked him for which i neva do n he has turned me dwn making exuses like watchin a film this has made me really worrired he isnt attracted t me nemore or heating what du u think n what should in do