posture

As the title says I had an chronic pain in my traps because of a strength imbalance in my upper/lower traps. Since I started training the lower traps its getting better slowly thou Im also doing the kelso shrug aswell to help improve my posture. I know that the traps are responsible elevation...

I've been working out, eating right and people are telling me they can see an improvement in my body. However, my friends keep telling me that I don't have good posture. I am frustrated about this. It should be a simple matter. I need some suggestions on improving this. Thank you for the advice.