I am 17, I just had unprotected sex about an hour ago. I know he got everything inside of me. My periods are very irregular, so I can't rely on them very much for anything, what are the chances that I'm pregnant? Can I take a test in a week?

You had sex, protected or not there is always a chance. The less protection the better the chance. You should go NOW, and get the morning after pill. The sooner you take it the better.

You are suppose to wait till your next period is due and if you miss it, take the HPT. But I would wait 3 weeks and if no period, take the test then, and if still no period, in another week.
Always use the first urine of the morning.

Yes, you could be pregnant. You had unprotected sex, so the chances are actually pretty good.

Like Chuck said, you can get the morning after pill. You had sex an hour ago, you're definitely within the time frame to take plan b, but do it now. Do not wait until tomorrow. Go to a pharmacy and ask for the plan B. Follow the directions exactly.

Where you are at in your cycle can increase the chance of pregnancy. Start at the First day of your last period, that means the first day you started to bleed even if it was just a little bit. That is the first day of your cycle. The best chance of a pregnancy is between your 12th to 14th day of your cycle. Your cycle is irregular so it will be hard to tell if your period is "late". You should see your doctor tomorrow and be honest. Ask for the "morning after pill". Other than that all you can do is what about 3wks and take a pregnancy test. I will keep you in my prayers. I do want to say one thing and please do not take this as judgmental because it is not meant in that way. If all turns out for you this time use this as a learning experience. Mistakes are lifes teachers. Everyone makes them. But it is how you use them that makes them OK or not. I hope you are able to come away from this mistake much wiser instead of a single mom. I hope the best for you.