I'm 21. I've had chest pains since I was little. My doctor said I was just wanting my parent's attention, but could there be something wrong?

It depends. Chest pain has many causes. This can range from muscular skeletal to heart attacks. Fortunately for you, blockages to the arteries of the heart are really uncommon in 21 y/o. Family history and other risk factors play a roll in early heart disease. There is a inexpensive outpatient ct scan looking at calcium score which could give you a handle on your risk factors if you are concerned.
Possibly. Chest pains in children and young adults usually are related to musculoskeletal aches and carry no real significance. In rare occasions they can indicate a heart problem. If the pains persist then it would be wise to consult your doctor who will evaluate you for heart murmurs due to valve trouble, heart muscle conditions, and heart lining inflammation called pericarditis with an echocardiogram.