Shoulders burning in daily activities

[strengt]

Dear all,

I have been lifting in the lower rep range for several years now.
I have this injury which nags the hell out of me, more in a psychological sense.
I am able to perform all lifts and exert power and force and speed.
The problem is my shoulders and sometimes not even those muscles alone will burn very quickly in daily activities.
I work in a grocery store and sometimes I need to clean shelves or sort selves , it varies sometimes but most of the time I get a burn very quick to where I need to switch arms or even rest. (pathetic)
This makes me very unhappy because what is the point of lifting weights and looking fit if you cant excercise this in your daily life.
Also I am a fan of martial arts and I shy away from the fighting gyms because of not being able to hold my guard up for too long and just not feeling competent with my shoulders like this.

What do I do?
I went to the physiotherapist and he said my injury was vague and he just gave me a bunch of Rotary cuff excercises which I performed for months, I got stronger on them. But the burn is still there.
It seems as if my shoulders have these invisible 1lb dumbells attached to them, I can also feel it when combing my hair.
There was some times where I would also feel a similar burn in my triceps when I would ride my bike this was when I was doing lots of push presses, I stopped doing those.
I suffer from depression, but muscles aren't supposed to be depressed right?

Please help me out.

[Mark Rippetoe]

Height/weight/age/current lifts.

[strengt]

Height/weight/age/current lifts.

height: 5'7
weight: 69kg
age: 23

Lifts 1 RM : squat: 115kg
bench: 100kg
deadlift: 140kg

[Mark Rippetoe]

Opinion on Boxing and thoughts about purpose etc.