Positive and Negative opk?

I have been testing since two weeks ago. I began using the Opk dye strips. I got 6 days of positives. Clearly way darker than the control line. Then I figured that maybe I should use the digital since I've heard the strips are more sensitive. The first day on the digital I got a negative. And now every day since then I have got a positive on digital and negative on strip test? 
I've been feeling very sick to my stomach. I also feel small cramps and very sore breasts. Typically my breasts are sore two weeks before my period. 
Any idea why I could be getting both positive and negative? And so many days of blinkey smiles even on the digital. I have yet to get a solid. 
Thank you so much for any advice!