How true is it that plan b can mess up your cycle ?

I just want to add that 2 weeks before your period is the most likely time to get pregnant, not a time you're safe.

Yes, Plan b can delay your cycle. If you are more than a week late, you should go ahead and test though. Plan b is only about 80% effective. Pulling out does zero to nothing to prevent pregnancy. DO NOT rely on your partner pulling out as a method of birth control as you will find yourself pregnant shortly. Men leak out sperm way before they ejaculate and they cannot feel and cannot control this leakage. If you truly want to be safe, you need to get yourself onto the Pill, Nuva Ring, an IUD or Depo-Provera-some reliable form of birth control. You can get this from your regular Dr or he may refer you to a gynecologist or you can go to a county clinic or Planned Parenthood etc. Anything between you and your Dr is confidential. If you ask your physician not to share information, they cannot tell your parents. You do not have to be any certain age to go to a county clinic or Planned Parenthood.