Skin darkening & hairfall. Should i do?

Hi doctor, myself Megha 25 years old, I used to have very fair complexion but from past some years my completion is degrading day by day, specially my arms, there are black spots on both of my arms near elbows and it's getting darker day by day,i hardly expose my skin in sun,but I think its getting affected by ac also , and the overall skin tone is also getting dark slowly, I apply sunscreen daily but still it's happening. My mom also suffers from same problem ,her arms and back is totally black now and I guess same is happening with me. What should I do? My dark circles are increasing day by day , recently I got all my blood test done like hb,thyroid, other hormones ,pcod everything was fine except vitamin d deficiency, I don't know what to do, I am also suffering from severe hair fall and hair have become very thin , my marriage is after 9 months , please suggest what should I do