symptoms... but too early?

Wednesday morning I felt crampy, so decided to take a litmus paper ovulation test, which came out positive. I was so surprised I got a digital one but that was negative. Hubby and I did the deed though anyway. Then Thursday morning tested again and the paper test and digital were both definitely positive. So we did it again that afternoon. Anyway, today my nipples have been soooo sore. Like unusually sore. And I have been light cramping on and off since we did it on Wednesday night. It's obviously way too early to test... even too early to have implanted. But I just feel different.... could it be? Has anyone just knew that they had conceived? We've been trying since 08/2015, but I don't want to get my hopes up.