At six months, you should have a GREAT relationship with your obgyn...if you don't...then, you cant' be pregnant. BOTH times I had kids, my wife and I knew the doctors very well, had their phone numbers, etc...why would you NOT give them a call at this point, about something like this???? I'm totally confused.
It's actually quite common to have some light bleeding at any time during pregnancy, however, you should never rule out complications - go to the doctor.
