I was having similar pain but more at 5 intensity and I went to see my physiotherapist. She assessed me for a disc issue. She told me that 2 standout signs of a bulging disc are that it hurts to sneeze or cough AND sitting is painful; both of which I had. With treatment it resolved to a great degree. Although I still have back issues, she has given me particular exercises and even 1 simple stretch for when I garden, for example and am in bad paid that really do help. Ice helps as always. Turmeric stirred into one's morning smoothie is good for inflammation (terrible taste but who cares when one is in pain, right?!). So I would recommend a good physiotherapist. I'd recommend mine but she's in Montreal where you likely do not live...
Pain in your stomach could be an unrelated issue...constipation? Magnesium citrate at bedtime every night for years works for me.
And your 'heart pain' if it does not radiate, is likely stress...muscles tighten and cause sharp pain. Another cause is dehydration. Drink plenty of water. Have you seen football players writhing on the sidelines at games from dehydration? It causes excruciating muscle cramps. Drink, drink, drink...and drink even more if you are on BP lowering meds that contain a diuretic. and have another drink of water for every cup of tea or coffee because they cause dehydration. And if it's hot out, drink even more!
Good luck! Let us know how things work out.