A month ago my left breast leaked oily substance than tonight my right breast did the same wat could this be?

Need more info. Difficult to say from the info you are giving. This could be just a normal discharge. The bast would be for you to have a breast exam at your GYN doctors office or general surgeons office and they should be able to determine from your history and physical exam if there is a bored for any further tests ( sonogram or mammogram)