confused....help

Posted here a lot recently but still so confused. cycle is usually 27/28 days. currently CD 12. cb digital advanced opk low. internet cheapie opks absolutely nothing on them. but.... ewcm for the last few days, cramping in one side, feeling bloated and migraine ( I have hormonal migraines so this would suggest a shift in my hormones) so why is there not even a faint line on the opk. cn digital there is but I am told you can't read the lines on those. HELP! thoughts please