The balloons are to infate inside the arteries to stop you bleeding excessively.
Of course you are worried, it was a traumatic experience and your consultant is dismissing you - they should instead be talking through your experience and reassuring you of what would happen this time/what they would do if it happens again.
I would write the following questions down in a notebook and ask them next time. Take someone calm and supportive with you if you need to.
What happened last time?
What is the correct medical name for this (was it placenta accreta for example?)
What are the chances of this happening again - I need a percentage number.
I am suffering from severe anxiety after the last birth and I would like to be referred to someone who can help with this
How will this birth be managed in the light of the last one?
If this happens again, how will it be managed?
If your consultant won’t answer, or brushes you off, you need a stock phrase like ‘I’m afraid just telling me it wont happen again is unproductive - I need to have more information, to understand what happened, why and how the next birth will be dealt with.’
It may also be worth asking for a birth debrief. Also avreferral to someone who can help with anxiety.
In terms of numbers it’s very unlikely you’d die. Without knowing exactly what happened it’s hard to say what the chances are of it happening again, but with your history they will be on high alert to any problems that occur.
Good luck.