Just out of practicality, your cycle can't come on the 15th of EVERY month, some months have 28, 30, or 31 days, so the one day difference does not mean anything. But the simple fact is having unprotected sex can get you pregnant. BC pills are probably what is causing your symptoms but I would be careful these next few months just to be safe.
I think that if you knew some basic information, then you would not worry so much. If you have decided to have sex, and it seems as if you have, then first thing first....keep it in mind that AIDs and other sexual diseases do not have an age limit and you are definitely putting yourself in harms way by not using condoms. No other birth control method will work and are useless in keeping sexual diseases away from you. Second thing is that once in awhile, some of the most consistent periods can change once in awhile. This can be due to any number of harmless things, such as changes in stress level, etc. And last, but certainly not least, you HAVE to be on birth control at least ONE FULL MONTH before it will keep you from getting pregnant...it takes it that long to even BEGIN to work, so if you are having sex then you are playing with fire as far as pregnancy goes. Most likely your "ache and pains" are coming from the hormones in the pill, but no one can say for sure. Hope this helps.
You should use Condoms as well as BC! Normally BC does takes 3 months to work properly. And have full effect. But NO birthcontrol is 100% effective and someone gets pregnant on BC everyday!
Oh and Btw, The pullout method doesnt work either. Because of pre *** I got pregnant on the Pill AND using the Pull out method. :).
Use BC AND a condom!! And the reactions are probably from the Pill
I really think you should be using condoms this month. The breast tenderness is probably a reaction to being on the Pill.
It's probably from your birth control, it can take some time for your body to adjust to it. You should be using a condom for the first week for sure but the first three months a lot of birth control will say it's not as effective.