Could I be pregnant?

My fertile days were Febuary 14-20. And me & my boyfriend had sex the 16, 18 & 19th. The risk of pregnacy was 15 %, 33% & 22 %. We used the withdrawal method & he pulled out before he was about to come. We last had sex the 27th & I'm experiencing cramping. I'm due for my period in about 4 days but I'm worried if the cramping is associate with pregnacy.