Hon, take a deep breath and calm down just a bit, okay? Let's address your fears one at a time.
First of all, the length of your menstrual cycle is determined by the number of days in your cycle, not by calendar months. So if you're counting by calendar months, then you may not be as late as you think you are, given that February was a short month. And really, menstrual cycles can vary at any time, particularly when you're young.
Now, on to the pregnancy risk. You can take a home pregnancy test. Anyone can buy pregnancy tests, they're not expensive, and most drugstores and even a lot of grocery stores sell them. We recommend buying two tests, so you can take another a few days later to double-check the accuracy of your result.
Now, if it turns out you're not pregnant, then everything's okay for now. But hon, do get yourself some reliable birth control, okay? Condoms are fabulous, we love them, and it's great that you're using them some of the time, but you really need to have a system of birth control in place every single time you have sex. We usually suggest using a combination of methods, such as condoms and birth control pills. You can get birth control pills and other forms of contraceptives at Planned Parenthood clinics, which you can find by going to their website: http://plannedparenthod.com
Go take a pregnancy test and see what it says. If you're not pregnant, then see about geting reliable birth control in place, okay? And also, you might want to check out this article: Ready or Not? It sounds like this is really stressing you out, and you might want to reconsider whether or not you're really ready to be having procreational sex at this time in your life.
And if it turns out you are pregnant, then you're going to have to sit down with your parents and talk about this, because hon, there's just no way you can hide a pregnancy, and you'll need their help in deciding what to do.
"The only unnatural sexual act is that which you cannot perform."
-- Alfred Kinsey