Unprotected/ help!

Have you ever worked with someone that you were attracted to, and had that "flirting" type of relationship? Well, this coworker and I have been flirting/ texting on and off for almost 5 months now, even hanging out outside of work, but always when other people were around.
Here's the catch: you could cut the sexual tension between us with a knife.
So the other night we went out just he and I, had a few beers (didn't get drunk) and when I was going to leave he kissed me... And then all the tension that has built up over the last few months was just released and we couldn't keep our hands off eachother.
LONG STORY SHORT:
I stayed the night at his house and we had sex 4 times. And he came in me every single time.. It was the best sex of my life, but because of getting caught up in the moment, we were both extremely irresponsible.
Yes I realize this was extremely irresponsible so please no hate comments.
My question is that I am about 4 days away from my period and was wondering if anyone knew the chances of me getting pregnant since I'm this close from a period and wasn't ovulating? It's been about 5 days now and I have the worst heartburn/ acid reflux imaginable and haven't ever had it before.
Also, if there's a chance I may be pregnant, how long should I wait before taking a test?
And how exactly do I go about telling him when our company has a very strict "no fraternizing with coworkers" policy?
Thanks for the input,
Sincerely,
Shit up a creek without a paddle.