You normally ovulate 10-15 days after your period not the next day. Unless you had sex again later its unlikely your pregnant. Wait until you miss your period and then test again.
^^I agree with aruth. And every woman is different. Both pregnancies I didn't experience any 'early pregnancy symptoms' until I was like 6-8wks pregnant.
Breast tenderness was my first sign of being pregnant. But, I was 3 weeks along. It's still constant for me. But I'd say it's too early for you to notice any pregnancy symptoms.
Not accurate actually aruth. Ovulation is typically around day 10-15 of the menstrual cycle, not 10-15 days after a period ends. Some women bleed for 7 or more days putting the end of their period just before ovulation, certainly close enough for conception to occur.
To the OP - if you're only on week 3 of your cycle it may just be too early to get a positive home test. Wait a few days to a week and try again with an early response test, use it first thing in the morning so your urine is more concentrated. In the meanwhile to be safe treat your body as though you are already pregnant. Take prenatal vitamins, they are most important in the earliest stages.
FYI - sometimes PMS can cause breast tenderness and especially if you are trying to conceive those minor symptoms can seem much more pronounced because you're hoping for them. I personally starting feeling "off" before my missed period in each of my pregnancies - I tested positive before I ever missed a period twice in a row (and have never taken a test for "feeling pregnant" without being right.) Good luck in your journey. Maybe you'll be back with good news in a few days!