What's Going On?

Lydia
The past 3-4 days I've been having a lot of stomach discomfort and lower back pains.
My last period ended on May 31st and ever since then any discharge I've had has been clear. But tonight I had quite a bit of dark brownish-reddish discharge and I was wondering what might be the cause of that? For anyone who can help, do you think my stomach discomfort could be related to that?