Accurate time for a test? Pregnancy anxiety?

Hi ladies. I am currently on the pill, a combination pill to be exact and I have been on it for over a year.

I just got into my first serious relationship (wooo hoo!) and my boyfriend and I rely on the pill + withdrawal method. I take my pill at the same time, sometimes I have been a few hours late but no more than 4 hours but it does not happen all the time, but I have never gone a day without a pill/missed a pill. Anyways, we had sex on the 14/15th of December and he may have not pulled out in time. Naturally I was freaking out but knew taking Plan B wouldn’t do much as I was already on the pill. However, I looked at my calendar and if I wasn’t on the pill this would have been my fertile and ovulation week so I am BEYOND anxious about being pregnant now.

I’m currently on my placebo week, I’m on the 3rd day and I don’t see a sign of my period. My boobs are sore and look bigger but that might be in my head? So basically: Would a hpt be accurate by now or when should I take one? Thanks for any advice you can give me. I appreciate it!