Pregnancy question about my girlfriend.

Ok, so my girlfriend had sex at least 2 months ago (before we started going out) with someone without using protection or anything. Since then, she has had her period and everything.Also recently, she has had to do allergy tests, where they stick needles in you to figure out your allergies. She was also rushed to a hospital recently because of an asthma attack, and they gave her morphine and stuff when she was in the ER.Now recently, she took a pregnancy test out of randomness and it came back positive. She took four more; two positive, two negative. She took one more after that and it was negative. Note that she has had her period in the last two weeks.Could the tests have said positive because of the allergy shots? I find it hard to believe it would be positive if she has had her period recently.

First of all lets get it straight. Your girlfriend had a period after her last boyfriend so therefore she was not pregnant by him. However she has shown to have a positive pregnancy test since your relationship which means you got her pregnant. She has had a period since the positive pregnancy then this is what we called a missed abortion, meaning she was pregnant but it did not grow correctly so she bled it out in her periods.
My advice to you is to get her on contraception and you to be more diligent and responsible to use condom every time you are fooling about or else you may have a child on the way. Ask yourself are you ready to be a father at this point and commit to this woman for life!