My LMP was on 25th Jan and now I am on CD50, still waiting for AF. I got a negative on HPT when I tested with First Response on CD 42 in the evening, there were no pregnancy symptoms nor PMS then.
Please help me before I take an appointment with doctor by answering or sharing any such experience with any of you.

1) I am TTC from 5 months and started with Stuart prenatal only since Feb 1st 2010. Has any one heard or experienced a delay in periods by starting a pre natal for the first time.
Never used any oral birth control.
2) On CD42, should I have tested with First Morning Urine for any possible positive result? I remember drinking a glass of water 30 minutes before I tested at around 6 pm.

Other details;
I got a positive on OPK on March 1st which is on CD36
I observed EWCM on CD 28
Have very sensitive nipples from a week now.
My usual PMS is soreness in breasts and sensitive nipples.
I have irregular periods varying between 30 to 36 days, but never this late!!!

Please help.