Suggest Treatment For Recurring Hyperpigmentation Of Upper Lip?

Hi, I suffered from hyperpigmentation on my upper lip abt ten years ago, after popping a pimple...it was very dark and very bad, but eventually went away after the use of hydroquinone. In october of 2010, this randomlly occurred again, without any apparent cause. It is lighter than it was the first time, and I am again using hydroquinone. However, it seems to look dark, then light, then darker..etc. if hydroquinone worked once before, why not now? What else caan I do? I'm so tired of wearing makeup., will thisbe a lifelong thing? Is there something medically wrong with me? I am 32 yr old, indian woman.