Why is my penis small on my penis head but gets thicker going down my shaft from the head, i feel this wont?

satisfy because i heard the womens vagina isnt very long so surely that means only my thin part of my penis will be inside her while the thick part is doing nothing :/ i measured and im proberly some stupid size on my head like 4 inch+ girth then down a bit to 4.7 then 5 then 5.2ish right at the bottom. help me out guys please. much appreciated.