That's a valid guess, honestly! Often, we'll feel what we're sure are pregnancy symptoms when they're actually ovulation symptoms. The best way to tell the difference is by looking at the calendar to see if it's near the time you should be starting your period, or if you just had your period a week or two before.
In your case though, it does sound like you're expecting your period within the next couple of days. If that's true, it won't hurt to take an early detection pregnancy test, especially if your symptoms aren't usual PMS symptoms for you.
If it turns up negative, then it's possible you're just having an especially difficult premenstrual phase (we all get them!)