When you start lifting gains come very easily. A new lifter can gain 2lbs of dry muscle tissue a month if not a little more plus increase in glycogen stores so one can easily come out with 4lbs of fat free weight each month for about the first year assuming diet and training and are point. Fuck I put on 40lbs my first 7 months lifting. Definitely some fat but a lot of muscle and a ton of strength. Then the next year that figure gets cut in half, and the next year it gets cut in half again etc until one hits their genetic potential and cannot make any further gains naturally or they're at a snails pace basicsllg unmeasurable. So in these 10 years have you put on 50lbs of muscle or so? If not your diet is off or your training. Dven if you're hormone levels were low and you were eating enough you would have atleast gained fat. You can still benefit from this "noob gains" if you get your diet and training dialed in. This gains are like gains from a steroid cycle. Hell id rather be able to gain like I could as a beginner then I do when I cycle these days. Just like what I told you about each year the rate of muscle gain goes down, it's the same with gear, the bigger you get the slower the gains come. I commend you for pushing on for 10 years without making much progress, I would have quit after 6 months. When I started lifting from day 1 I spend all my time reading about diet and training so I wouldn't waste any time. That's what I would suggest you do. Just read read read all about nutrition, different training methods etc. you'll grow. Get your test levels checked also. If they're low and you restore them you'll be amazed on how quickly you progress. You're 40 so there's a pretty decent chance you have low t. Go talk to your doc about some bloodwork. But diet is the most important thing.

What's you body fat? Have you had any blood work done?