The Snapping Technique For this - Tie a simple band on your wrist. Whenever you feel that you are thinking too much or going deep down on thoughts. Just Snap the rubber band on your wrist and more hard you snap it the more it will be of help. And then after Snapping your brain gets alerted and alarmed that you are overthinking. Next step is, now that you are aware and know that you shouldn't overthink. Just replace these thoughts with another one or concentrate on things happening right now. You can also perform other task like reading a book or going for walk. It is a method based on scientific research. You can google about it for detailed information.

You are having mild anxiety symptoms. It can be very common during stressful situations. If stressful situations are not present and you are worrying for every small thing, then you might be having mild anxiety disorder. Mindfulness Therapy/Tips can help you. If severe, then visit nearby Psychiatrist. Good luck.

Do a thyroid profile test. And consult a psychiatrist