I am guessing , since I don't have a photo, that you have developed Female Pattern Hair Loss. This has become the trend in a lot of women, because of stress at work and home and due to unhealthy lifestyle (bad eating, sleeping habits and no exercise). So start MODIFYING LIFESTYLE. It will help naturally prevent future thinning by controlling your hormonal levels. And trust me, it works like magic. Also, you will need long term treatment with prescription based medicines thus a visit to the dermatologist is needed. And remember that hair treatment takes a while and depending on the extent of hair thinning you will get a result. Don't get frustrated.
Next Steps
Visit a dermatologist near you (allopathic). Don't fall prey to those hair clinics and advertisements. Before you choose your dermatologist just read http://www.skinmatra.com/#!Skin-Troubles-Here-is-WHAT-NOT-TO-DO/cmbz/5779118d0cf2d54ad62a8b1e
Health Tips
Do not use creams or 'treatments' suggested by friends or family or pharmacists