Dear bleeding on brushing is classical sign of gingivitis which was due to yellow layer on your teeth
It lead to periodontitis
No its not that much serious it is just
You can loose all the 8 tooth where yellow layer is present because of periodontitis
Due to periodontitis you are at
Twice the risk of heart diseases
Twice the risk of
diabetes
And many more diseases
On the question do you need cleaning
I am answering by another question
Q: would you like eat in a plate in which same amount of yellow (rotting foods and other things) matter is present
What ever your answer , i will not
Each time you eat that rotten things going into your body