Or you might just be running, walking and squatting a lot. If your hips are constantly tight and it's affecting your flexibility, think about doing more strength work on your bum so that it is doing more of the work and taking the impact out of the hips.
This is a great hip opening yoga sequence from Yoga Journal. Roughly 25 minutes. Do all of it, or some of it, but hold your pose long enough to release some tension and tightness.