What Causes Irregular Periods With Nausea And Light Headedness?

Hi

last month I came on my period a week early, It was very light untill three days in when it became heavy and continued for a further four days. This month I have been light headed, every morning I feel like i have a hang over when i haven't been drinking alcohol also I have been really hungry and eating lots. My period is due today but as yet no sign. Could i be in the early stages of pregnancy? My partner and I never use contraceptives, he always pulls out just before he ejaculates. We have been making love like that for seven years and had no scares.