If someone would be able to answer this for me....I have been trying to diet and quit smoking

so of course I tried with some help...

o.K. A lot of help. I started off taking "smokeaway" and while on that started taking several different types of diet pills.
I have not had a period since august, and have taken several pg test and of course "negative"

. Could all this medicane cause me to have a neg. Result or would it just throw my period completely off? I pray I am pregnant...But I do not want to overlook any other possibilities either.
I have already found out that my colposcopy and leep would not effect it to this degree..So any advise or information would be greatly appreciated. :d