Don't sweat it, you're doing just fine.
Without surgery you won't be able to add an inch to both your measurements, or half an inch. All you can do is avoid artery-blocking habits like smoking and poor diet and encourage good cardiovascular health by regular exercise.
The good news it that according to the statistics at The Definitive Penis Size Survey, your length of 7" is very close to the 72nd percentile, meaning you are as long as or longer than 72% of others, roughly. Your circumferece of 5" is right on the 50th percentile so you are right in the middle.
If you look at numbers from non-self-measured studies such as Lifestyles Condoms, you're doing even better.