What may be happening
Your brain may be treating a small amount of uncertainty as a safety threat. Even after you check, a doubt appears: what if I did not really notice? That doubt feels urgent enough to send you back.
Why it feels hard to stop
Each extra check can feel like proof that checking is what kept you safe. The relief is real, but it is temporary, and the next doubt often arrives faster.
What can help
Make one intentional check. Notice the sound of the lock, the feel of the handle, and the visual cue that it is secure. When doubt returns, practice referring back to that first check instead of starting the loop over.
When to get support
If checking takes significant time, causes lateness, creates distress, or expands into other reassurance behaviors, a therapist familiar with anxiety and compulsive patterns can help.