Thank you for your question.
Symptoms like mood swings, hot and cold, nausea, fatigue, etc are all symptoms related to hormonal changes.
Hormonal changes are very common in ladies and can happen due to excessive physical or emotional stress among other causes.
The black clumps indicate clotted blood or old blood.
It happens very commonly and is not something indicative of anything serious or anything to worry about.
It should settle as your periods come to an end.
If, however, you have excessive bleeding, you should be seen ASAP as excessive non-stop bleeding can cause anemia (low hemoglobin and red blood cells) that can be dangerous.
Let me know if you have more questions.
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