Why wont my car go in revers?

i got stuck in the snow today and it was working and my boyfriend keep puting it in drive and reverse to get me out then all of a sudden my car would just reve up like its in nuteral can anyone help me and tell me what i can be i hope its not my transmisson goin out please help me thanks so much oh and its a 1990 oldsmobile custom crusier station wagon if that helps any