What Causes Secondary Amenorrhea And Vaginal Dryness?

I've had secondary amenorrhea for almost 2 years. It started when I began competing in fitness and was required to reduce my body fat to extremely low levels. Since then, I've experienced vaginal dryness, and occassionally, light bleeding after intercourse. I also developed a very bad case of acne (I've never had skin issues in the past). I'm not currently taking any oral contraceptives. Are my symptoms a result of a decline in estrogen? If so, what can I do to resolve this problem?