2 periods in a month? (females only, please)?

Has anyone ever experienced 2 periods in a month? One was normal and began on the 3rd of Jan 11 and ended on the 5th. My period is usually around that short, so I wasn't overly concerned. I had another period on the 27th. It lasted just about a day and a half, and was very clean (no clots etc). Needless to say, that's a bit early. I've had some nausea this month but I usually get that with my period, so no biggie, once again, but I've recently been experiencing some feelings of being light headed and dizziness for the past week or so, and that is not normal for me. I also have been having headaches and light cramping throughout my abdomen, with the lightest cramps being along the sides and the worst in my lower abdomen and in my lower back. I'm sort of embarrassed to admit this but I should. I had unprotected sex with my partner on the 13th and the 14th. I'm not saying I could be pregnant because I'm aware that the symptoms mimic so many other things, so I'm also looking at other scenarios such as hormone fluctuations and such. Has anyone ever experienced any of this? I would not be asking, but I'm still having cramping, nausea, headaches and feeling light-headed intermittently and it's been almost a week since that period, and I never have period symptoms after my period. Any help or insights would be appreciated. Thanks.