Thanks for your question on Health Care Magic. 
I can understand your concern. 
Since you are having left 
chest pain and 
nausea which are associated with eating, possibility of 
gastritis and GERD is more. 
But better to rule out heart diseases first. So get done ecg and 2d echo. If both are normal then no need to worry for heart diseases. 
For symptomatic relief, do following things. 
1. Avoid hot and spicy food. Avoid junk food. Avoid large meals, instead take frequent small meals. 
2. Avoid 
stress and tension. 
3. Start 
proton pump inhibitors and prokinetic drugs. 
4. Keep 2-3 pillows under head in the bed. Go for walk after meals. Loose weight if you are obese. 
Don't worry, you will be alright with all these. 
Hope I have solved your query. 
Wish you good health. Thanks.