how do u die of bloodloss?

It would not be painful because you would pass out before you felt pain (assuming you are very rapidly losing blood).

You die because the circulatory system cannot continually supply your cells with the nutrients you need.

I believe the main cause of death is because of heart damage. The cells of your heart begin to lose oxygen levels. Because of this, they cannot carry out cellular respiration-->therefore toxic levels of metabolites build up--> the nerve cells and become irrevocably damaged--> the heart cannot beat--> same process occurs with the rest of the cells in your body.

Like the heart cells, brain cells also undergoe this same process, dying after not receiving oxygen for about 4-6 minutes.

Your blood carries the Oxygen in your body. No blood and the body pretty much suffocates.

Well blood loss mostly means that you don't have any blood pumping to your heart or your brain and that will kill you. You have to understand that your heart pumps blood to itself as a way of sustaining its oxygen in its own muscles.

In some other instance, you could lose blood flow to one of your legs and in that case, the leg would basically die and you'd have to get it amputated. But if it's blood loss in general then none of your body is getting blood and the main worry is your heart which is what provides the brain and itself with blood. The most painful part of course will be your wound, you won't actually feel the blood flowing out of you. You'll become very weak and as your brain stops getting oxygen as a result of your heart not being able to pump, and you'll basically pass out briefly before you flatline.

To my knowledge, your heartrate would not increase because your heart is getting little blood and therefore will have less energy to pump

if u dont have enough oxygen your heart rate begins 2 quicken alr? but blood loss is the actual physical escaping of the blood from the human body