Odd bleeding may be TMI!

[Mulberrystreet]

I've come on here for some advice as I'm a bit puzzled as to what's going on.

Have just finished a course of antibiotics for BV. On the second to last day of taking them I notice a pink tinge on the loo roll when I'd gone to the loo. Since then I've been bleeding for about a week, except it's not normal period blood, it's very brown, almost black and is mainly clots and very thick.
I'm on cerazette and have been for 4 months following having the implant out. About 3 weeks ago I had some regular bleeding which I sometimes experience when on cerazette, however this had been over for a few days by the time the new bleeding started.
I should add that the antibiotics also gave me thrush so I used a canesten pessary, not sure if that is anything to do with it.

Anyone have any ideas? Is this normal or should I book in with my GP?