Sex can push your period back
I am the same age as you and it happens to me a lot as well. If you have done a test and it is negative don't you worry, your period will come! Sometimes thinking about it too much is worse. Of you want to be surer go to the doctor though
I was 10 days late before with pregnancy symptoms of all kinds but the post above is correct don't stress too much my af came sure enough stress and a variety of other things push it back good luck
Thank you! I will try not to stress!! :)