Abnormal bleeding?

Currently I am taking Ortho Tri-Cycline Lo. I have been on it for about 6 months I would say. Unfortunately I have a very hectic work schedule (I'm a paramedic) so I  am unable to take it at the same time everyday and yes, just like every other woman in the world I sometimes forget. I have had a normal period, painless, just a nusense. Within the last few months, I have been having a "period" twice to three times a month and they are painful!! Cramps, back cramps, head ache, THE WORKS. When I'm not on my period or one of the weird bleeding sprees I seriously feel like I'm PMSing all the time. I'm moody, irritable, backache, and light cramps. I am not sure if this is a birth control issue or if it may be something more serious. I have to wait two weeks to see my doctor, and would prefer to not go to a clinic. So ladies, any advice or peronsal experiences?