The thoughts are not you and the scenario they present is not real.
Think of your body as a house, and your brain as the alarm system within the house. The alarm system is there to alert us when there is a potential threat such as somebody breaking in. When the alarm system goes off, we react by waking up and doing something to protect ourselves.
Living with OCD is like living in a house with a broken or hypersensitive alarm system. A few drops of rain, a car driving by, or a bird landing on your window can trigger the alarm system. Unfortunately, your alarm system cannot determine the level of threat. It cannot differentiate a gust of wind or an intruder. It is programmed to keep you safe, so it will alert you of all potential threats, big or small.
Anatomically, your Amygdala cannot determine if a threat is real or fake; therefore, it shoots out chemicals such as Serotonin (the neurotransmitter thought to be responsible for regulating our mood, appetite, sleep, and sex drive), Adrenaline (our fight or flight response) and Cortisol (our stress chemical). These three chemicals are what give us the physical symptoms of anxiety such as feeling jittery, rapid heartbeat, sweaty palms, shortness of breath, and an upset stomach. Since we are instinctively wired to pay attention to these physical symptoms, we immediately want to do something to relieve the anxiety. This may look like excessive checking, counting, questioning, washing, or any other reassurance seeking compulsive behavior. We engage in compulsive behaviors because we feel uncomfortable; however, we are reinforcing the obsession by engraving it deeper into our neuropathways. This vicious cycle only makes the OCD worse. The compulsive behavior may be helpful for a brief moment, but ultimately, it is harming you by strengthening the obsession.