period is late due to just started taking medication??

hi my name is shane and i had sex with my gf on the 3/17/07 and her period date was the 28th and she still never get it yet it is the 3/29/07 also she is on this new drug that helps her concentrate in her work the she just started it 4 weeks ago to this date is the 3/29/07 the amout she takes varies in the first week it was 10mg and slowly went up as she go used to it now she is taking 40mg's i was wondering if this could be a factor of a miss period or could she be pregnant she took a pregnancy test but it tested negative well i hope you guys can help me out iam kinda freaking out also its our first time and we used protection also well thanks for taking out your time to answer my question thanks........

I'm not sure what medication your girlfriend is on, however sometimes it is normal to be a few days or even a week late for a period. There are many reasons for irregular periods (from the obvious pregnancy, to stress, diet and many other reasons). If you have a question about her medication do a google search and see what you can learn about the effects or as a pharmacist.

im not an expert but ill try to help... everything that imortalone said is true but you also said that it was ur guys first time. i have heard that the first time a girl has sex can affect her period because her body is going to changes and trying to adjust to them.(my first time i was a week late) also if she stresses her self out thinking that shes pregnant that can also affect it.....i hope i helped just a bit good luck

yeah is was stressed out on being pregnant but yeah thanks for your guys help

oh yah the medication that she takes is strattra it went up from 10mgs to 20mgs to 40mgs over the 4weeks that she was taking could that be the problem? thanks