The size of my erect penis pressing fat pad :6.9" and when no pressing:4.7". i need to lose 88 lbs. after lose weigth will i see 6.9" usable length?

Maybe, maybe not...: Penis size is not the only or main reason to lose 88 pounds. Lots of factors related to penile size-genetics, nerve function, vascular health, hormones, other. The sooner you start losing weight, the sooner you will look and feel better (which also is a factor), and decrease the aggravating effects of obesity on BP and blood sugar/diabetes ( which impact erectile function).

Obesity and Men: I am not sure you will see all of the nearly seven inches, but weight loss will definitely bring you more visible length to your erection.