Question: Are you checking this when trying to hold the same position in the water column, or ascending? The difference could be air expanding in the legs of your drysuit as you ascend, which could be hard for you to vent. That happens to me a lot, I'm a new drysuit diver.
Other than that, lots of AL tanks like to ride really butt-light in the water at lower pressures so that could be adding to the issue as well. In that case it could be possible for you to adjust with body position alone: extending or flexing the legs, putting your arms out in front ala Superman vs folding them across your chest, even head position makes a difference.
If none of those work, it could very well be a matter of weight positioning. If you have thigh pockets on your drysuit it could be worthwhile to move some ballast to your pockets. Fins can make a difference as well. Scubapro Jets are fairly negative compared to many other fins and could provide the needed weight on your legs to keep you from going head down.
Some more specific information on how your rig is setup could probably help other troubleshoot the problem much better than I am able to.
Peace,
Greg