First time using opk's NEED HELP!

Kellie
Soo another app told me to use an opk 12/6 cycle day 9, I did it was sooo negative. Took another 12/7 in day faint pos line but it was there, at night it was positive, line was dark. Took another about 12-15 hours later in fear I read it wrong and maybe it wasnt dark enough, 12/8 in morning another positive dark line.
EWCM 12/8-12/9
Watery CM 12/10
Sore erect nipples 12/8- 12/10 (no sore erect nipples today 12/11,)
Severe cramps w/ left side pain 12/10-today 12/11. 
What day do I use for ovulating 12/7 or 12/8? Note: irregular periods, cycle lenth 26 days and started using Vitex this cycle.