I have returned home 3 weeks ago from a summer working abroad. While I was there I had sex twice, once with a failed condom, so I got the morning after pill about 5 hours later. I got my period then about a week later. The next week I had sex again, with protection. Now I am home I am now 10days late, and am usually very regular. Could it be the change in environment, the morning after pill or the fact I am now back athletic training that has caused this? I am very stressed over it so maybe this could be a reason either? Anyway all help would be appreciated thanks.

First of all, calm down. I know it is hard but I've been in your position before and stressing only makes it worse. To help you calm down a little, take a pregnancy test. If it's positive, you have a decision to make and if it's negative, well you can relax. That should help it come and don't forget there are a lot of changes in your life so that might be the reason. If you still don't have your period next in a week or two, you should go to a clinic and get a doctor's pregnancy test.
Just remember to relax!