Suggest Treatment For Sun Tanning

hi!!i overexfoliated my skin 3 yrs back..after that my skin got tanned considerably..i consulted a local dermatologist n was prescribed melacare..after using that i got my skin tone(4 a few days only) back but my skin became susceptible to sun exposure..it cud no longer resist sun n my skin got tanned again!!i want my fair,sun resistant skin back!!plz help