I was on laughing gas today and it felt like i died or was dying. is this a normal sensation?

Nitrous oxide: Laughing gas is a mild sedative or anti-anxiolytic. The gas is only active while you are breathing it, effects lasting only a minute once off. The effects are usually relaxation. Downsides are occasional nausea, and some women have vivid dreams. The only explanation i've for your experience is the claustrophobic feeling of the mask used to give the gas, another form of sedation may be best for you.

It is normal: Laughing gas or nitrous oxide can cause euphoria and hallucinations so those feelings are normal.