Ulcerative colitis can be associated with other forms of autoimmune conditions like rheumatoid arthritis which presents as joint pain, stiffness, most commonly seen in young females like yourself. Also prolonged sitting and screen time can lead to sustained incorrect posture which goes unnoticed and can lead to mechanical symptoms like backache and neck pain.
Next Steps
Get and Xray of cervical spine ap and lateral. Also if symptoms are too much better to get evaluated for rheumatoid arthritis. CBC ESR
CRP RA FACTOR, anti CCP are confirmatory blood tests for rheumatoid arthritis.