Breakthrough bleeding with b.c.?

I just finished my first pack of tri-cyclen birth control....I didn't take any of the placebos (7) and got my period when I should have...I started my next pack last night, when I should have, and now I'm bleeding again this morning? Is this just breakthrough bleeding? Sorry if this is a dumb question but this is my first time using b.c. so I'm not quite sure what to expect. Thanks!