Hello ultimate x,
Thanks for posting your pics and the info about the doctors you've seen. That's definitely the right step - to get a physical exam. It's a good sign that there are no lumps under the nipples and that the ultrasound came up clear. Have you had them take blood to run your hormone levels? Testosterone and estrogen, when imbalanced in the male body, can cause male breast growth. It may be in the very beginning stages where you're feeling things happening in the breasts but physicial tests like a manual exam and ultrasound still show nothing. If there is a hormonal issue at the root cause of the pain you've felt in your breasts (and before the breast growth starts to become visible), you should find out if you have a hormonal imbalance. Looking at your pictures, you don't appear to have gynecomastia at this time, and the physical exam by your doctor thankfully confirmed that.
All the best (keep us posted!),
Dr. A