Feeling nauseous but on my period

So I have just one question but I'm going to go into detail so I can get the best answers possible! To start off with I am almost 21 years old and have not had a regular period since I first started when I was 15.  I have not yet been to an OBGYN, which I know is bad.  Me and my boyfriend where together for 5 and a half years and just recently broke up at the end of November 2010.  We had sex the second week of November and did not use protection but it was one day after my period was already done.  I have heard that it is impossible for a women to get pregnant that soon after her period so we figured we were ok.  So all of December goes by and I had no period, during which I threw up the last 3 days of December and carrying on until January 3 of 2011.  The last week of December all the way until now (January 5) I have either thrown up after I have eaten or felt like I had to throw up. I am the kind of girl who will resort to doing everything possible not to throw up so I would have thrown up the times I was nauseous if I hadn't.  Now I just started my period on January 4 but it was normal... it was brown in color and not very heavy at all.  My normal periods last between 8-10 days and are rather heavy the whole time.  I did not think I was pregnant until the beginning of January because I was still feeling nauseous and throwing up.  Before I thought I missed my December cycle from stress over the break up.  I dont know why im still feeling nauseous, light headed, head aches, sleeping way more than I normally do, meaning going to bed at 11 and some days not waking up until 2 pm.  So I guess I am just wondering if theres still a possiblity if I am pregnant or is it something else.  Thanks

[Gabradean]

I meant my period in January was not normal... had a typo!

[mooksmom]

Why not do the smart thing~~~go and get a home pregnancy test!
Do not believe any of the 'old wives tales' people tell about time and pregnancy possibilities. You can be on ANY day and get pregnant IF there happens to be an egg waiting. If you have no regular periods and are experiencing nausea OR have a different type of period and nausea...do the pregnancy test.