The constant worry can cause you to be even later. So easier said than done. Stop worrying. If you find a planned parenthood you may be able to get some additional testing. I can tell you that sometimes weather can change your cycle as well. Go find out. Look for a life clinic in your area as well or Free testing clinics. Let me ask you when you say that you are worried that you could be pregnant or worse... What is the "worse" equate to?