My shoulder always is sore?

Possibly rotator cuf: Most common shoulder pain is overuse causing rotator cuff syndrome which ranges from mild tendonitis to complete tear. You should get complete clinical evaluation and possibly xray and/or MRI depending on exam findings.

See orthopedist: Shoulder pain can be referred from the neck or it could be locally from the shoulder. Common local problems include but not limited to arthritis, bursitis, impingement, rotator cuff tear, labral tears, biceps problems, stiffness, and instability. Common volleyball related issues are: instability, biceps and labrum problems in addition to partial tears of the rot cuff. See a shoulder orthopedist.

Get evaluated: Severe shoulder pain could have multiple causes including infection, nerve compression, overuse, trauma, and even a neoplasm. A physical examination and diagnostic imaging will likely be necessary.