Joint and Tendon pain after Chemo and while on Herceptin

I'm 5 months on now but still on herceptin. I continue with joint stiffness but as I'm on letrozole now I also get hand and feet stiffness which improves when I start moving again.  All my muscles get tight easily and even after walking or standing a lot my calves go tight. It's hard to know what is causing it but I do know for me if I remain mobile it improves.