weird pains and opks

Hope
Last night i had very weird pain in my uterus on the eight side, it wasnt painful but it made me jump atleast, the pain lasts for 2 seconds but it kept on comming for atleast 2 hours. I have mild AF like cramps and i think its the witch comming tomorrow because im 13dpo. I took an opk just now and its not positive but its darker than yesterday. I ran out of hpt thats why i took opk. At 8dpo i took an hpt and gor faint lines but then at 11 dpo i got a bfn.