Have missed 2periods, but test show's i'm not ...

Sounds to me like you should see a doctor. First off, have them run a blood test to confirm that you are not pregnant. If it is a negative, then ask the doctor what it could be. Maybe you have some kind of hormonal imbalance or if you are under a lot of stress at the moment, that could be it.

Get a  early pregnancy  test  ,Wait  until  the very first  time  you  got  to  urinate in the morning...When you  do  take  your pregnancy test then  And  see   what  the results will  be

For example:  You  get  up   Nov  29, 2009  at  8:00 a.m.  needing   to  urinate , And that  is the first time  you  got up , Take  your  pregnancy test than

For  example:  You  went  to bed   10: p.m.  You  got  up  3:00 a.m.  you  got to  pee , take  the pregnancy  test   than...

They  say  the  very  first  urine  has  alot  to determine   whether  you   are  pregnant  or not

there are several causes for missed periods - check below:

http://www.menstrual-cycle.info
http://menstrual-cycle-health.blogspot.com/

Go to the doctor for an ultra sound on a dead fetis. Now!