PCOS , TTC, IMPLANTATION BLEEDING?

Recently I've found out I have PCOS and have been on Metiform for about 2 weeks. Not long enough to actually have an effect on my period , i don't think . We've been TTC for 10 months and this is the first time ever That I've had dark almost brown blood with a more mucus look to it . Since I have PCOS my cycles are never consistent any more . I was wondering does implantation bleeding come and go? And what does it look like ?