Jon gave you great advice. It's very true that women can have different symptoms then men. We're all so different. I did not have the common symptoms, but, I did have a lot of what I thought were stomach issues. I was also very tired all the time. You are young at 42 but you do need to find a way to get checked out. My sister had her heart attack at 45. It's better to know what's going on. It could be stress and stomach issues or it could be heart related. Please keep us up to date on what you find out.
This is one of those times that you must find a way to get checked out. Women have different, more subtle symptoms of heart disease than men. Mild chest discomfort or none at all is possible along with back pain, fatigue and nausea. Because you have the number one risk factor, being a smoker, you need to get checked out. Call a local hospital and ask about your situation, they may have a program for you, but don't wait until it's too late.
Jon