I can feel my heart beat strongly ( mostly while trying to sleep) and have noticed a pop in my chest when taking a deep breath, or while stretching.?

This can be normal.: A strong heart beat is normal in an otherwise healthy 30 y/o person. When you take a deep breath, you increase blood flow to the heart and this may be perceived as a pop sensation. If your feel your heart skips a beat, or your pulse is greater than 100, on a routine basis, you may want to seek the advice of a primary care doctor and have your thyroid checked. Best wishes.