"Self love is a sin"
I think that a bit of an overbroad statement.  "Inordinate" self-love, according to Aquinas, is where the sin lies.  It is love of self that causes man to seek a good or avoid an evil; sin arises when one has an inordinate attraction to a good (food, for example) or avoidance of an evil (pain, for example).  Scripture is also clear that self-love is expected of us, else we cannot love our neighbor.  There is a proper way that man may love self.
Self-abuse, however...