Well, symptoms of getting ill as well as many other things. I would just wait a week or two and if you get more symptoms and you don't get your period I would pick up a test from the dollar store. GL!
Most likely it's just pms, but it is still very possible you could be pregnant. I would recommend that you wait a week after your expected period to get the most accurate result, just in case you had a longer cycle than normal, or something.GL!