Does Exercising Cause Delayed Periods?

Hi, I have a recently missed my period, as in i m three days late and i have had sex, but we ve always used a condom and it s never broken, and i have a lot of period symptoms (slight cramps, discharge, backpain, swollen breasts) but nothing has happened. I think it might be because i starting lifting a lot of weights in the morning and then doing hard cardio at night, but i m still a little nervous, i m almost 80% sure i m not pregnate but i just i dont know