Assuming your cycle is 28 days (the average) then you will ovulate around the 14th day of your cycle. If it's the 12th day now then you are bang in the middle of your fertile time. You are most fertile for the 3 days following up to ovulation and the after as well. You are not pregnant yet!!! The sperm are waiting at the ovaries for the egg to be released! If your boobs are sore, this could be a good sign that you are ovulating now.
If your periods are regular you should know the day your period should start. That very day, or to be even more sure, the next morning, use your first morning urine to test. Any earlier and you may get a false negative.
Good luck and I hope there was enough baby dust with you this month!