I help people solve this problem everyday in my practice. The key is to improve your hip capsular mobility and soft tissue extensibility in the position of hip extension with internal rotation (https://www.youtube.com/watch?v=ZkzFT6rRMhQ) and then reinforce that shape with some neuromuscular re-education as  seen in the video. Then obsess over this mobility practice for about 20 hrs and you will begin to see that your gait will become more natural with the “feet straight” position. The key is to remember to keep your feet straight when you walk. 

Best, 

Mike Caisse, PT, DPT, Movement Specialist, Mobility Certified Specialist, Crossfit L-1 Coach