Reminds me of my first "dude, you're balding" remark. But mine came at the age of 17!!
Sorry to say this but it does look like you're thinning on top. Even under a strong light, you still shouldn't see that much scalp when your hair is at that length.
However, you're still young and you still have a good amount of hair to work with so it's good that you caught it early. As stated already, jump on finasteride to go with your nizoral. If you're lucky, then it will thicken up your hair. But you must be patient. finasteride thickened up my hair but I only noticed a difference after about 10 months into it.