Hello mam, thanks for trusting health care magic.
In my opinion as your urine pregnancy
test is negative get a pelvic ultrasonography
and b HCG
testing because it can be an early pregnancy or worse ectopic tubal pregnancy and then visit a gynecologist with reports
exercise can cause delay of periods definitely but its good to be double sure.
And from next cycle onwards start using a regular method of contraception
In case you have further questions you can consult me on health care magic forum and i will be happy to help
My URL is http://bit.ly/drmanishajain
Take care and wish you all the best.
Dr Manisha Jain