Spotting on Cycle day 24?

My last period was on Jan. 30 and Im not expecting my period until saturday. The spotting was only 2 or 3 drops and was about the size of a penny all together it happened just after cramps on my lower left side which was a stinging felling and lasted only about 5 minuets or so.. The only time i had unprotected was on the 12th (CD 14) my usual ovulation is around CD 16-21 the only other time i had was the 18th and 19th but we used protection both times but their might have been some sem*n that had gotten inside of me b/c the condom broke on the19th. But if it was implantation it couldn't have happened that fast so I know that I shouldn't be pregnant. Is their a chance that my ovulation has changed and i did ovulate on CD 14 which is when I had unprotected ? The blood was a pinkish red color from wat i could tell. Last time i got pregnant was around this time last year and i lost it but I never had spotting or anything like that the only symptoms i had was increase in discharge, and i was sleeping more than normal which made me realize that i could be pregnant and that's when i took an HPT after i also realized my period was 2 days late. What can cause you to bleed like this just before your period is due?