I may be 8 months pregnant! have some signs but still don't know

I am almost 17 and me and my long time boyfriend had unprotected sex in november. I didn't know that a guy doesn't have to cum for sperm to be released. After we had sex i was 2 weeks late and thought something was wrong.....iv never been late, but when i got my period i thought everything was fine. unfortunetly i got a bad cuncussion and got post cuncussion syndrome from that and as a result i don't remember much. i do get my periods although i don't remeber if i am late or if i do skip periods. I have had a very 'straight' stomach and over the past months i have gained a stomach that looks like i am 3 months pregnant. its not big enough to be eight months tho but i am relitively small. Resently one of my older friends got pregnant and iv noticed that the symptoms were the things i was going through before. like morning sickness. I have been having losts of pressure in my vagina area like somthing has been pushing. I have gas bubbles in my stomach and i heard it is the feeling of kicking. my breasts hurt extremely bad and have grown. i have bad back pains. my boyfriend bought me a pregnancy test a couple weeks ago and it came out negative. but hearing so many women be pregnant and not know it has been freeking me out. PLEASE HELP!!!! %-) %-) %-)