Am Having the same problem But found the cure....BIOTIN VITAMINS!
You can buy them anywhere~I buy mine at walmart for $3.00 a bottle wich has lasted me for 2 months....I have been taking them for 2months & I have near hair growth already!! Not perfect Thick hair but that will take time....So give it a try ~there is no known side effects either of this vitamin....So thats great!~I felt ugly when my hair was thinning ~now after 2 months I feel like me again........GIVE IT A TRY!!!GOODLUCK.
http://www.bodybuildingforyou.com/vi...hair-loss.html (this site has some info about biotin~And it's talking about use for men But ...I couldn't find the exact site I went too...But this has the same basic info.

BUT the question about Prenatels, I take them and I am not pregnant. I was prescribed them from my doctor because we are going to try next year if I can get my weight under control. :| They are making my hair grow crazily fast and is super thick now. :O I have to get my hair cut every 5 weeks compared to the every 10 weeks. :| lol But talk to the doctor.