I seem to be around 4.1 girth, and it really sucks from my perspective. I've had a number of girlfriends and quite honestly I don't think any of them had a problem with it, and in fact I'm continually told I'm awesome in bed (for a variety of reasons). However, recently my now EX gf (what a bitch she is) totally reamed me on my penis size, saying several mean things, including I have "no dick", and it's the smallest she's seen in her life. To make matters worse, she was telegraphing to me she didn't enjoy the sex for at least two months because she would make comments on how she loved huge dicks, etc. She sleeps around a lot, and I'm sure she's seen the whole gamut of penis sizes, so it really depresses me that she says I'm the smallest she's ever seen. Not sure if I believe her, but it sucks either way.
However, even though I'm probably around 4.1 girth, it seems like if I jelq for 30 minutes before sex, and then pump, and use a cock ring, my girth goes up significantly. I think it easily jumps to 4.5+. This isn't (currently) permanent, but who cares. If the girl I'm with doesn't think it's weird that I "pump up" before hand, then what do I care? It also gives me hope because my penis is a real "grower". It's very small when limp, but it grows to 6" erect, and the girth is gaining. From what I've read on here, I might be able to gain 1" in girth, maybe more, over time.