Hi, I had the same dilema and this app: bit.ly/FreeAppEnglish helped me to understand it ! It's interesting to note that, although both "if I were" and "if I was" are descriptively correct in subjunctive statements (though "if I were" may be considered more "proper"), only the former allows conditional inversion: "Were I to win the lottery, I would buy a private island" is fine, but you'll never hear anyone say "Was I to win the lottery, I would buy a private island" (even though you might hear someone say "If I was to win the lottery, I would buy a private island").