Okay well my body is really strange for some reason when I turned 20 my period started to be very irregular. My last period was in November of 2011 and I finally got it my period in August 2012 but it only lasted two days and the day after it ended I had unprotected sex. Can I still get pregnant? And when can I check if I am if I have no clue when my next period will come. Help!

Yes you can still get pregnant. Since your periods aren't regular you have no idea when you're going to ovulate, so every time you have sex pregnancy is possible.

Wait 3 weeks and try testing. Do keep in mind false negatives are very common, so if it's negative wait a few more weeks and test again, or see a doctor for a more accurate blood test.

Have you seen a doctor about your irregular cycle? You really should find out what's going on to cause this. While you're there you should ask your doctor about going on the pill, it will not only help prevent pregnancy (help, not 100% guarantee), but it may also help regulate your periods, depending on why they're so irregular.

Good luck.

Agree, pregnancy can happen and testing every three weeks for two or three times should confirm.