i fuck on average once a day...sometimes more and rarely with the same person...my cock is 10x8 but the other person doesnt normally know that until i she takes it out to suck it...i blame my sexual encounters to my face and personality, but i blame my awesome sex and extremely satisfied customer on my cock...
as far as the pain goes when i shove my cock in...i just ignore the complaint and keep shoving...it will evenually strech out...i mean its supposed to push out a baby...i sure it will take my cock...
also i find if you are hurting her just put it in her ass... she might not normally like it but at least it hurts less...she'll get over it.
(not to mention...you can always go balls deep in the ass)