Don't worry about it, you are well within average. I don't remember the last time I saw a guy any bigger than you in a locker room, or any other mature scenario. The global average is 5 inches erect, only a small percentage of above average men bring that number up to where it is; the majority in fact fall under it.
I've known many men who are ''plagued'' by remarkable reputation's of prowess in the bedroom with women, who were only 4 inches erect.
I decided to answer because I felt we were at rather opposite ends of the spectrum and you might value my response. I am fairly lean, over 6 feet and my penis is 8 inches long flaccid, I only grow an inch or so when erect..but of course I can shrink nearly any length given the right circumstance's, like anyone else.
Ultimately, I don't really care about ego boosts..I did when I was younger but when you mature you realize the truest values aren't so petty. I think I would have to wonder why my life was so horrible that I needed to draw pride, self esteem confidence and personal fortitude from the meagre reception of 'genital' praise, or incessant difficulty with any form of penetrative sex.
I once had to console a long time friend who saw me naked when we were changing once, who was the same size as you flaccid, 1 inch; roughly 8 times smaller than my own. I was used to the shocked reactions" but rarely am I so obligated to concern myself with their insecurities after they realize its possible for men to be that large. I said its normal and he probably won't ever see another as big as mine as its so rare, but I do I have feelings of insecurity myself- and I am still self concious about my penis, but for different reasons..there is no winning in my opinion.
Also don't watch porn - I don't say that to shield you but to enlighten you; its in no way an accurate depiction of anything in the real world. Its a product that's created in part by a huge number of efforts to deceive its viewer and feed into their fantasies, fetishes etc.. Pornstar's are not as large as advertised, and the average penis can be made to look enormous given a modicum of applied photography/filming knowledge.
I tried the warm towel trick, never honestly figured out if it ever did work or not. I think it might have a little.
You got a lot of growing time if you lose some weight as well.