What Causes Persistent Pain In Chest Extending To Sternum?

I have had ongoing pain and what feels like movement under my left to cage for several weeks. Pain is not sharp- more dulled. It seems to extend to sternum and setimea feel it in middle of my back. Have gained 15 pounds in last year and am struggling with perenopause and food cravings. I don t know if they are related. I was a smoker, pack a day for about 26 years. I no longer smoke but do Vape, and am afraid it is something bad. I was treated with Avelox 3 weeks ago for a sinus infection.