Hi, I Had Unprotected Sex Last Month Although He Ejaculated

Hi, I had unprotected sex last month although he ejaculated outside I am confused right now as I am an irregular period. More of spotting. I have done a urine test myself and it is negative. I would like to state here that I just finished a dosage of a med called lonart. Could there be any correlation? I felt all the signs I get during ovulation but my flow is not regular in any way. Kindly help. Thank you