could i be pregnant even though ive had a period?

before my last period whilst in my local chemist i suddenly went really hot and faint and felt like i was going to throw my whole stomach up but wasn't actually sick. when i am ill i am very rarely sick i have been heaving alot and have been sick several times over the past 3 - 4 weeks. the day after my period finished i had a positive pt. but i took 2 more after that came back negative. now i am getting more discharge than usual frequent headaches and stomach aches that feel like period pains but im not due for my period yet? i have been trying for a baby for over 12 months advice would be very helpful thanks