Second positive opk this month?

Megan
I got a positive flashing smiley on my digital opk the 13th. The 15th I got the solid smiley face on my test and I confirmed it with a non digital opk that was without question positive the 15-17 morning. 17th evening the non digital was negative. I was excited everything went as expected this month!!
We are away and just because I am still figuring out my cycles I took another nondigital opk test today the 19th and it looks positive, with the test darker than the control but not as super obvious as before. I know you are supposed to stop testing after a positive so should I just ignore this one? It's just making me confused!! It's def too early to be a positive suggestive of pregnancy. My only ovulation symptom I've had every month is sore nipples which started the 15th and still continues. 
Has this happened to anyone else and subsequently did your period start two weeks after the first or second positive opk or did u get a bfp?