Why do i have blood clots?

I think I know what you Have my aunt died from something like that they could not find out right away what is was. When they did the autopsy they found out. They had the women from my moms side go get checked 2 of my cousins had it. I know I can find out from my mom every one thought it it was cancer. Its not it is some type of blood disorder where it cause blood cots to form and they break free. Those clots travel trough out your body blocking arteries and doing a lot of harm. they can cause Heart atacks stroke and a lot of other problems. The lump in your might be blood clots.