Question: I have low self esteem, and been obsessed with my appearance the past 3 years, doubting my sense of style or my beauty, comparing myself to others in general what transits or natal placements explains this.

Astrological perspective.
Doubting=Sagittarius your own appearance=1st House and obsession=Scorpio about this doubts. Also Sun-Mars conjunction can be a manifestation of self-destructive behavior.