6 days late, cramps, yellowish discharge

My fiance and I had sex on my fertile window, according to the app. We had sex for about a week after that. No protection, we used the withdrawal/pullout method. Now, i constantly feel some period-like cramps but no period just yellowish discharge. And I also feel some pain on my back on the lower left side.
Am I pregnant? Should I be concerned about the discharge? 
Thank you for any response.