Hi Sehlen -
A couple things could be going on. One is possibly some hip instability in your right side that you aren’t aware of. If you can have someone video tape you running away from the camera, then straight back, you can see if there is any ‘hitching’ going on. It’s possible you may be weak in the glute medius/minimus on that side - many runners are weak in those areas, especially if you sit a lot. Good exercises to do are clam shells and abductor strengthening, and there are many more you can find online.
When you are leveling your pelvis, make sure you are not introducing extra tension. You need to engage just enough to create stability. The more you lean (in going faster) or going downhill, the more you will feel that ‘reverse crunch’, but don’t overdo it at easier gears. Try this: as you are running and engaging your dantien (low abs), completely let go and feel what that feels like. Then lift your pubic bone just enough to stabilize the area. You might find it’s less than you need.
Good luck and keep us posted!
Certified Chi Running and Chi Walking Instructor