Are you irregular? If so how long has it gone on for?

I've been irregular since I started (17) and I'm now 20. I know I should go to the doctor but I keep postponing it :/
​I missed my period for one year once so that was strange. And when I get it sometimes I get really bad lower back pain and It lasts about 10 days ?. And sometimes I bleed when I don't have my period.....