It went off 3 times again last night. I will check the sensor pads today. I also still have his cot propped up from when he had a cold so I will take the books away as it may be a combination of both.
When he was really little the full alarm went off twice one night. We rushed in and he was fine. We then adjusted the sensor and it has been ok since (until now).
I need to take DS to the doc next week actually so I will mention it then.
Thank you