First of all, I'm very, very sorry for your loss, and for all that you went through last year.
I read tons and tons of post about the "not feeling able to breath or heavy feeling in the chest" before I had my c-section. I was VERY freaked out about this. I could handle everything else I had read...but this scared me to death.
I ask the doctor when I was getting my epi about this issue. He told me that this will happen if they give you the eip or spinal and then lay you down too quickly. The fluid will travel upwards and give you that heavy can't breath feeling. If they keep you up longer and then when they lay you back, keep you at an elevated angle, it does not happen. And....it didn't for me.
You might want to ask your doctor about it and express your concerns prior to having the spinal.