Really worried!! Brown period after normal period

Has anyone else experienced this? 5 days after my period I have another period dark brown bleeding, cramps and back ache. This has been going on now for 3 months but never this dark brown. I had a termination 3 months ago due to the baby having anencephaly Everything was fine before the termination. Just really worried and wondering if anyone else has experienced the same thing?

Thanks in advance