I take 2x concerta 36 mg a day, what possible risks do i take with this and could this be the cause of my sleeping problem and stress ?

YES IT CAN BE: Any stimulant can cause sleep disturbance, especially long acting such as concerta, the trick is to take the least amount, take weekends off, avoid caffeine and take it as early during the day as you can, you may also take melatonin at night if problem persists ot switch to strattera (atomoxetine) which is non stimulant and doesnt cause sleep problems.

Yes: Concerta , as a stimulant, can indeed affect your sleep and can also causes or increase feelings of anxiety. You are on a fairly hefty dose for an adult, and it may be your dose needs adjustment so you are not experiencing so much side effect and still get the benefit you need for your condition. As with any med, weigh how much it helps against how much it hurts to decide whether to keep it as is.