I was studying is correct if you are taking about the past (past continuous tense), but if you are using a conditional (second conditional) in the if clause or Wish, you can use both "if I was studying... or if I were studying..." or "I wish I was studying... or I wish I were studying..."

I was ... You were ... He was ... We were ... You (plural) were ... They were .... English has so many irregular verbs. I suspect you just have to learn them.

I was El were lo usas para el subjuntivo O para you they o we Si quieres mejorar sientete libre de agendar una clase. Saludos