The ovulation cycle is very responsive to multiple internal and external stimuli.
As you have mentioned, stress could certainly play a role. This could happen in many ways. For example, not eating well as a result of the stress - altering your body's nutritional status might influence your period. Similarly, a change in your sleep-wake cycle (such as working nights) may do it, as your period is in part tied to your body's sensing of light-dark cycles. You could start by trying to establish a more regular, normal work, exercise, diet, and sleep routine. If this resolves the problem, then this is probably all the thinking about it you need to do.
However, if this does not resolve the issue, then you may want to see your primary care doctor
or your OB GYN doctor. This is because sometimes changes in the menstrual cycle may be related to another underlying medical condition. For example, alterations in the levels of thyroid hormone in the blood are very common, and often produce effects on the menstrual cycles.
Your doctor will perform a thorough physical exam and, based on the findings, will recommend whether or not you need any further testing.