Suggest Treatment For Dark Inner Thighs

I am 21, 5'5, 50kg and no medical history, i have dark inner thighs, really dark ones and once i applied a lightening cream to it and what i got were huge stretch marks and darker inner thighs, its so embarrassing that i cannot undress in front of anyone and this has even affected my relationship life... please i need help... what can i do? I cannot apply creams because the one i applied as practically ruined my skin with stretch marks and rashes... what can i do now? thank you