I feel like my body is going crazy; need advice. I know this is long.

[glassfields_]

My story starts the month before last, about two weeks before my period, when I began experiencing mild pregnancy symptoms, such as very slight nausea, mostly during the afternoon, tiredness, short-lasting headaches, and very sore breasts which kind of seemed to spring up from nowhere. I didn't really think that much about it, and I wasn't surprised at all when I started my period, although I normally experience severe cramping, bloating, and a bit of a breakout on my face, and none of these were present at all aside from a very dull cramping that only lasted for a few minute just once.
I was, however, surprised to find that my normally 5-6 day period only lasted 2.5-3 days. It was also very light, and just pink and brown, with very little red. I never bled through a tampon, and when I thought I should change it, it was uncomfortable to pull of because it was still dry for the most part.
I was also confused when I kept experiencing pregnancy symptoms after I quit bleeding. Not only this, but more of them, and at a higher intensity. Smells started to make me sick as well as the continued waves of nausea in the afternoons. I felt sick if my stomach was empty or if it was too full. I kept peeing every 20 minutes, and my boobs, which still hurt, got blue colored veins all over them, which made my chest look bruised at a distance. I decided to take a pregnancy test during this time, and it came out negative.
I figured I must be getting sick, and I forgot about being pregnant, but at this point, my symptoms were at the worst yet.
I started this last period exactly a month from the last. It was lighter even than the last, was completely brown and pink, but lasted 3-4 days. The day after it totally quit, I spotted pink just once in the middle of the day.
That was just a week ago. Currently my existing symptoms are:

waves of nausea that come and go all day, in cars, when hungry, too full, or around certain smells
frequent peeing, waking up at all hours of the night to pee
feeling tired, forgetful, and clumsy, tripping over my own feet
gassy
bloated by the end of the day to where I look pregnant, but during the morning, my stomach is flat although I can feel a small, semi-hard bump below my bellybutton. I'm insanely skinny, and don't have enough fat on my stomach to pinch, yet when I suck in, the bump stays.
I've never gotten headaches until all of this, now they come and go frequently.
Strange dreams
sore, swollen boobs with blue veins
One breakout after another. My skin is normally clear besides five days before my period. This is just a new breakout after the last starts to go away.
Really light cramping.
Still bloated at night.
I've put on 3lbs, which doesn't sound like much. But when you're 15-20lbs underweight and have spent the past two years trying to put weight on unsuccessfully, that is out of the ordinary.
I've also in this past week, gotten a nagging lower back pain that I cannot get rid of no matter what I do.

Now, I might add that I'm NOT tying to get pregnant, but I was irresponsible and had unprotected sex. I'm also 20. I'm under no stress currently whatsoever (actually, besides this, everything has been going great), and I'm not on the pill. I'be never been to a gyno. I'm a full time student, so I'm on my parent's health insurance which makes a doctor visit regarding a possible pregnancy to be out of the question. Actually, she has noticed these symptoms too and asked (not happily, either), if I was pregnant.
So, pregnancy symptoms and a regular period seem to be two very conflicting things, hence why I've posted the topic in 'other' instead of 'pregnancy'
Could someone give me some possibilities as to what is happening to me? I'm actually pretty desperate.

[glassfields_]

I took one a few days after the first bleeding stopped, and it was negative.
I read on the internet somewhere that girls who bleed while pregnant are usually the ones that have low levels of hormones and false negative tests. I also remember hearing from a friend's mom that she bled with all her pregnancies, and a doctor told her it was more common in underweight girls, which she also was.
The guy is my boyfriend, and has been for the past year and a half. I haven't said anything to him just because if I'm not pregnant, I'll feel dumb and also I'll have stressed everyone out, and disappointed my mom for nothing.

[Clysta]

Sounds a lot like it could be pregnancy. It sounds like the bleeding you had wasn't an actual period, but rather just vaginal bleeding of some kind. Have you taken any pregnancy tests? If not, it would be a good place to start. Regardless of how your parents feel, you made a choice and pregnancy is the consequence of that. You NEED to get yourself in to see a doctor and if you are pregnant, you need medical care. Are you still with the guy? You should mention (if you haven't already) to him that you suspect you are.