It is never too late to change anything in your life.
The age you mentioned, in this day and age, is still young and life could hold a lot of nice things for you up ahead if you look for them. Do you have any hobbies? What do you like doing? What interests you? Walking is very good, both for the morale and for the heart. You could join a rambling group in your area. If you like reading, you could join a book club where they select a book to read, then you get together to discuss it. It is a way of meeting like minded people. Or you could go to you local Library and see what is happening in your area. You could even go along to one of the Colleges and get a prospectus with a view to joining a class that would interest you. Music is also very good for the soul.
You have carried out a service to the public for their good - now it is time to be good to yourself.
You seem to have a good GP, one who was not prepared to take chances with your life and who was prepared to refer you to the right people for tests. Whether precautionary or otherwise. I think he acted in your best interests. You seem to be in good hands.
Please do not despair, there are a lot of good people out there who will be willing to communicate with you and help you in any way they can.
Ally, is correct. There isn't much to add but have you posted with the depression, anxiety forum? If you are being treated for the heart chest pain (angina), does the nitrate medication help you?
Many of us on this forum have made lifestyle changes, added exercise and better diets to improve our heart function. And there are many interventions today that help improve the blood flow, as well as so many mdeications to aid in this. No, it's not too late. Keep us posted on what they find. You'll be able to see how well the other posters have done. Take care, Ally