M i pregnant?

Patient: Hi, my usual period cycle is more than 28 days, but my previous 2 cycles are 27 october and 25 november. I had unsafe sex on 17, 18, 19 and 20december. No doubt he evajucated. But i have heard that pre-eva sperms can also cause pregnancy. I do have mild spasmic pain but i have not got my periods till today i.e. 25 december. Could you please tell me know that i am pregnant or what can i do to stop it now.