I don't think the morning after pill is that good for you that often , but i'm unsure. If your really thinking about this a lot that can cause stress and stress can definately make your period late. I know there were times I seriously thought I was pregnant and was late , but as soon as I did the test it was such a relief to see neg. And my period would come literally that day , within hours. A few months ago I got a positive but I was also 14 days late so I already kinda knew I was expecting. So although I got sidetracked a bit there , the point is stress can cause you to be late. If your late and getting a couple of negative results , you probably arent preg. But it still could be too early to tell. Your best bet is drag your ass to the doctors and find out for sure.
False negatives are much more common than false positives so get it out of the way darling!
And if you aren't pregnant use condoms and bcps .. Taking the morning after pill a lot cannot be that good for your body ... If you dont want to get pregnant , protect yourself.