periods and plan B

So I had to take plan B for the first time 10 days ago, my fiance and I have been just experiencing a little bit of unprotected sex, just to start, but unfortunately he got a bit excited and experienced some premature ejaculation, knowing that pre cum can contain sperm I began to panic and that's why we both decided that plan B was a good option for us, we want to wait on children after we're married. my period was set to start December the 3rd, and with everything I have read most women end up having there period being late after taking this pill, however mine ended up being a day early. I'm just curious if this has happened to anyone else. I'm assuming if I were to be pregnant there would be no period at all, just wondering if this occurred to any other ladies?