I'm 18, and i have a hunch back is their anyway i can fix it?

Yes, but...: If it is flexible, it may improve with posture exercises (consult with a physical therapist; you may need a referral from a physician). It it is stiff, changing the curve (called kyphosis) requires surgery. A spine deformity surgeon can counsel you on what is involved. It is not a small procedure.

Get checked : If this is just not a result of poor posture, it could be secondary to a spine deformity like a scoliosis or kyphosis which can be readily evaluated by a spine surgeon who can tell you what your options are and whether a surgery would be indicated for your degree of deformity if present.