You are suffering from hormonal changes causing Androgenetic alopecia causing hair fall. It's completely stoppable even regrowth of hair is possible with certain medications without any side effects. Treatment depends on the grade of hair loss. So, it's a must for diagnosing which grade, you are in for an effective treatment. Please  send photos of your head, by direct online consultation for accurate diagnosis and proper treatment.

No...it is a water soluble vitamin and overdosage is very very rare. But biotin alone won't give good result...there are specific tablets for it.... kindly consult online with relevant photographs for proper diagnosis and management.