Yes, it is possible. There is actually a possibly reason why this could be happening besides bad luck.
The female Pokemon of the two you are breeding has an 80% chance is passing her ability to her baby. This does not apply if you were using Ditto. So if you were breeding two Pokemon and neither of them were Ditto, then look at the female. If she has Sturdy, then this explains why you are so unlucky.
If she has Heavy Metal (the Aggron line's Hidden Ability) then the chance of 60% of passing Heavy Metal down is 60%, which means Sturdy and Rock Head each have a 20% chance of being the baby's Ability, which is the same as the previously mentioned situation.
If either of those situations were you, then that explains it. Otherwise, the number is 50% and you were unlucky.