my period has practically stopped ?

Hey I was wondering if someone could help me. I'm just 18 and am experiencing extreme nausea and a very short period. I've been with my boyfriend for 6 months now and the only form of contraception we use is a condom (tried 5 different pills and none if them agreed with me). I came on my period yesterday and it was really different to a normal one I didn't get much cramping and I wasn't as bloated as I usually am. Last night I was feeling really sick and nauseous and vomited in the early hours of the morning, now I've had food poisoning before and if felt like that so all today I've been thinking i just have a mild form of food poisoning until I noticed that my period has practically stopped and I only have a few spots of blood. Now I'm worried, could I be pregnant? or is my mind running away with me? I've always made sure that the condom hasn't broken after intercourse, so I'm really confused. Any advice is good advice, so please help! ):