total knee replacement 6 months ago?

I had total knee replacement in Feb. I done great throughout recovery, but now I seem to be feeling a lot of stiffness , which I know it to be expected but now my new knee seems to feel weak to me . I had hoped it would make me better. I don't have the same pain, but I don't feel all that great and confident with this new knee yet. I spoke to my physical therapist and he said it could take up a year for the knee to "feel ' like mine. That it is a long recovery and takes time. And to just continue with my exercises. I get down hearted sometimes I had hoped for more progress by now, I want to walk again without feeling like I am going to fall cause my knee gives out. And sometimes it feels like it so stiff when I am walking. Just want to know if anyone out there has similar issues with a total knee replacement, Thank you