I'm going to say that based on the info you gave me, it's pretty unlikely that you're pregnant.
In order for you to have conceived, and based on the timing of your sex, you would have had to have been ovulating during your period, or shortly after your period ended. This isn't usual. Most women ovulate around two weeks after the start of their period.
That's not to say this can't vary. In your case, I'd bet that you just have a light period. The reason you're feeling weird is that you're probably about to start ovulating, which can cause some unpleasant symptoms. It is just as PMS and our actual periods can, since we experience a rise in hormones during ovulating. (Honestly, when ARE WE NOT prone to feeling weird with all of these hormonal shifts?)
So here's the scenario where you could be pregnant - and keep in mind it's unlikely but still possible.
It's possible that your "light period" was implantation bleeding, if you had unprotected sex a couple of weeks ago as well.
If you didn't, I would just keep on keeping on, and only take a pregnancy test if your period is late.
However, if there's a possibility that you conceived before your last "period," then now would be a good time to take a pregnancy test.