You're right but it goes further. The hips are also affected by the jaw and neck. If you're tight in hips you're quite possibly tight in Jaw and neck. You can massage the jaw easily with your fingers. For neck raise head up, then down, then left then right for 30 mins to release.

Also try, Cossak squats for opening hips. Don't be scared of doing high reps. 300 opened mine up but 30 wouldn't have been enough. Just body weight.

If you want to get to the more root problem then focus on diaphragmatic breathing. We shallow breath alot and this leads to problems in joints.

Beyond that it's probabaly stress as you mention but these actions can work through it. Start with the physical and move to the breathe when ready.

Hope that helps!