Irregular Periods. On Microgynon. Having Dark Brown Discharge. Pregnancy Test Done. Can I Conceive?

I'm 22 years old, me and my partner have been trying to conceive for the last 2 months and since this I have had problems with my periods. The first month I completely missed out a period then it finally came but was a normal period, this month I started having dark brown discharge for a few days when my period was due thinking my period would arrive then this continued but i started having bits of blood with it, now it has been just over a week and im having very light bleeding. I have no pain no cramps. I'm not sure if this is my period or not, I have taken a pregnancy test and it was negative, now im worried it might be something else. A few years ago I had brown discharge now and again which my GP said was hormonal imbalance where i took microgynon for a few months but i havnt taken this for two years and my periods have been regular and normal since we started trying to conceive. I'm worried that the bleeding wont stop although there isnt much of it.