Thanks for your question on Healthcare Magic.
I can understand your concern.
If your pain worsening with movements, breathing, coughing etc then possibility of
costochondritis is more.
And if your pain is worsening after eating hot and spicy food then possibility of GI related pain is more.
In my opinion, you are mostly having costochondritis. And yes, it can affect
sternum and diaphragm bone.
So follow these steps for better symptomatic relief in costochondritis.
1. Avoid movements causing pain.
2. Avoid bad postures in sleep.
3. Avoid heavyweight lifting and strenuous exercise.
4. Sit with proper back and chest support.
5. Take combination of painkiller and anti inflammatory drugs.
6. Apply warm water pad on affected areas.
Don't worry, you will be alright with all these.
Hope I have solved your query. I will be happy to help you further. Wish you good health. Thanks.