possibly pregnant or just weird symptoms?

Hi, I am 18 yrs old and I have been having sex with my boyfriend only using the pull out method.  I have been off of birth control for 5 months and my period was back to normal.  I have never been late or missed a period before i got pregnant last year and not since i had her.  When i was pregnant i had a little bit of light spotting when i was about 7 weeks along.  My period for June came 10 days late, however a week before my regular period was supposed to start and the week i was supposed to be having it i got a few really strong lower abdominal cramps like i sometimes do right as im starting my period i also had increased vaginal discharge with a brownish tint.  Just without the period.  I took a few pregnancy tests and all were negative, then i went to the doctor on the 10th day.  That same day i started having a stringy mucusy period.  Im not quite sure that it was my period it was much lighter than my regular period and started out brown and then changed to light pink tint, when it is usual bright red, but most of it only lasted 3 days and then 2 days of very very little brown stringy stuff (regular period 6-7 days, with 4 days of heavy and 2 or 3 light days).  After it all ended i started having bad abdominal cramps occasionally again, fatigue, sore breasts, headaches, nauseasness, and occasional dizziness.  My doctor did a blood pregnancy test and it came back negative.  I also just feel pregnant, when i lay on my stomach it just kind of feels like i have a full bladder all the time like it did with my first pregnancy.  Also i just started to notice this past week that when i lay on my stomach i get an intense headache and kind of dizzy and as soon as i sit back up its gone.  This is completly weird to me i have never had most of these things.  With my usual period all i get is some mild cramps every once in a while.  All my doctor wants to do is put me on birth control.  But I dont want to risk being pregnant and it effecting the baby.  With my first pregnancy i had major complications she was three and a half months early and i lost her when she was 4 and a half months old.  So i am very hesitant to start birth control again.  Also the last time i was on it it caused me frequent headaches.  Also the only positive hpt i got with my first one showed one dark line and one light line, could that mean that i had kind of low levels of hCG and maybe the same now just earlier and or an even lower level.  Im just looking for alittle advice as to what people think i should do.  Im just scarred to do the wrong thing. Any advice would help.