Should i see a therapist (short question)?

If the mirror thing was more serious, than yes. Since you said you don't think your ugly, you dont have BDD (body dismorphic disorder) which makes people see themselves as monsters in the mirror, when in reality they don't look like it at all. The whole thinking things are lies is not an issue, it's actually a sign of intelligence, to question things and have your own beliefs. If the mirror thing gets more serious then you have to go.