Hi K.,
If I were in your shoes, I would surely feel concerned. I did take YAZ, although it had the opposite effect on me. I didn't stop bleeding on the stuff. I hated it!!!
I would recommend seeing another doctor. Especially if your doctor hasn't run any tests to see what's happening inside your body. Focusing only on your instincts, how do you feel? Do you sense a problem or another pregnancy? I've not ever heard of one's period stopping while taking a BCP... an IUD, yes. I'm not a health care provider, but that just seems a bit off to me.
If you would like my doctor's name and number, I will glady share it with you. She has delivered both of my children and she is in a class all her own. She is such a beautiful hearted and understanding woman. She NEVER stresses and has never made me feel that way. She feels more like a sister or a dear friend than my OB/GYN. I just love her to bits!! And, for me, those appointments are ones I never welcome... When my husband and I moved to Orange County 7 1/2 years ago, finding an OB/GYN was a worse concern for me than finding a place to live in less than 1 day! I think I was absolutely blessed in finding her. In my opinion, YOUR doctor's concern of how your feeling and what you're thinking and going through must be as important to them in knowing and understanding as it is to you.
Until you find out what's going on, I would progress forward from this point on as if you are pregnant (if that's even a slight possibility). You wouldn't want to do anything to jeopardize the baby. And just to touch on the fact that your pregnancy test read negative, so did mine at first when I was pregnant with my son.
In Light,
J.