I doubt very much if you are pregant, for a start it is very unlikely for you to be fertile on the first day of your period, you will be more likely to be fertile 2 weeks after your period. Your period is actually your body flushing out the last uterus lining that was getting ready for the last possible pregnancy. So your body hasn't even had time to produce another egg yet. If your pregnancy test says negative then i'd say you are in the clear. Don't even worry about it, do another test if you are concerned, but I highly doubt you are. Next time don't ever rely on condoms alone, I believe they are absoulutley useless for contraception, they may be useful for protecting you against std's, but that is all. Use the contraceptive pill to be certain, or some other type of contraceptive device. Your doctor can advise you of every option and tell you which one is best suited to your type of life style and health concerns. Good luck !!
Suzy