light brown discharge??

On the 31st I had sex without a condom, but I'm on birth control but I've been taking my pill 1-2 hours earlier than my normal time because I was on vacation and there was a time difference. My period is supposed to start tomorrow and I've been having light brown discharge lately, I was looking up what it could be and some said it could be implantation bleeding while others said it's normal for this to happen before your period starts. I'm just really worried I could be pregnant, so I'm wondering what you may think it is... I've just been so stressed about this😰