How do you know if your birth control is working?

I am 25, just get back on birth control after a few years of person off. I've be having profusely of breakthrough bleeding this first month. Today I finished the last of my alive pills for my first month and I had unprotected sex today. It say that you are protected after the first 7 days. I'm just worried because I'm hoping I begin my pills at the right time. (My periods be very irregular). Has anyone else be nervous give or take a few this or am I just worrying over zilch?
Answers:

=[ idk..?

you should probably be ok i used to forget my pills alot and didnt get pregnant but i guess everyones body is different i wouldnt worry nearly it to much

I'm just curious. I'm a soaring woman. I'm 5ft 11 and weigh 215. I wear size 16 in clothes.?

i haven't be on birth control for a long period of time so i really can't utter to much. But if you really are worried give it a week and turn to the store and buy a test. no involve to be worrying about it for a long length of time. You will feel better if you know for sure. just try not to stress your self out just about it. you will feel worse.