No Sin Excludes a Religious Vocation
Is it too late for me to discern a vocation to the religious life after mutual masturbation?
Not at all. Religious life is a life of conversion and repentance. St. Augustine of Hippo, the great father of religious life, lived an unchaste life, which on his own account included both natural and unnatural acts with his concubine. But his conversion was precisely to the chastity of religious life.
What is important to keep in mind, though, is that you must have a sincere and constant desire to be chaste and to practice chastity. If your habits have been overwhelming or especially disruptive in your life, you need to discuss this with the vocation director or directress of any community you may wish to join, or at least discuss this with a confessor. But in and of itself, no sin excludes from religious life, since the religious life itself is for those who have been converted from the world, from sin, in order to follow Christ more closely.