Soreness of the breast can occur in pregnancy
though it can also be seen just before and during a period as well. Pregnancy tests
detect the HCG
hormone . This hormone is usually detectable by day 11 to 14 after conception though some tests may detect it slightly sooner. IF a test is done too early then it can be falsely negative.
If this is the case for you, then you should repeat it in a few days, when this time period has passed. When at least 2 weeks have passed, it can be redone. If the test was done at the appropriate time then it is truly negative. If the test is truly negative and the period remains delayed then the other causes of delayed period would need to be considered.
(1) pregnancy tests detect the HCG hormone, this is not detectable till day 11 to 14 after conception
(2)may need to repeat the test if it was done too early
I hope this helps, feel free to ask any other questions.
Dr. Ivan R. Rommstein, General Surgeon