What just came out of me?? (Sorry it's gross)

So I chose to not have my period the past two months (just messing with my birth control a bit, which the doctor told me I could do) and I was supposed to get my period this coming Tuesday... I got it a week early, this past Tuesday, but it has only been like that weird brown sludge.

The past couple days I have had cramps that seem to be worse than what I am used to.

Today I went to the bathroom and this weird thing (?) came out of me? I was just wondering if it is something I should be concerned about.

I am sexually active but had a negative pregnancy test since the last time I was.

I'm sorry it's a gross pic!