Can I stil have pregnancy hope?

Today is CD 21 5-7 dpo, I had a blood pregnancy test done and it was negative. I have had cramping go from one side to the other and a twinge/pull type feeling in the middle lower abdomen. I have a history of ovarian cysts so I am trying to keep high hope as I know that can make a difference. But with the Blood test negative I am starting to get depressed. Should I test again?