Is it normal to get your period a week early while on the pill?

I've been on the Tricyclen Birth Control pill for over a year now. Two weeks ago on a Sunday (which was the beginning of a new pack) I had accidentally skipped three days of taking the pill, so on the third day I thought it would help if I just took the two pills that I missed on that day, plus the third pill. Between then and now my boyfriend and I have had our regular intercourse (without the use of a condom, except for yesterday because I was put on an antibiotic for a sore throat, so I wanted us to use a condom since we as women know what most antibiotics do to the effectiveness of the bc pill). During the time I've noticed that for about the past 2 weeks my nipples have been feeling sore and tender (my right one more so then my left). And now today I've started my period a week early (today also marks 1 year that my boyfriend and I have been 2gether Very Happy :D
(I read in another topic posted in this section of the website that getting your period early can be a sign that you're pregnant. Is this true?) [I do NOT want to be pregnant!]