Early period, breakthrough bleeding on tricyclen Lo?

I went on Tricyclen lo when my son was 6 mths, before I tried for him I was on the reg. tri cyclen and it worked great, my periods were 3 days, always at the same time, no issues. Now since ive started the Lo, I get my period 1 week before my sugar pills, so i have a 2 week period and only 2 weeks off, im going to my doc, to ask herr opinion, but wanted others experiences, have you had issues with the Lo, or do you think it could be related to still post partum issues, my son is (almost) 9 mths, so I doubt it has anything to do with it, but I wanted to be surre before switching back to the Reg. Thanks in advance