What Causes Light Menses With A Blood Clot?

i am having my period. it has been a bit odd. day onestarted brown and mucusy very light..only showed when I wiped after using the toilet. then it stopped for a day.. then actually period blood started red normal still light some what. while i was doing sit up i head a popping sound very light and something came out of me. a clump ended up in the toilet..it look like turkey inside but dark red and bloody. what is it?
thanks