Sweetie, you do have to tell him how you feel. And if he doesn't listen, well, he never will, so take that not as a hint but a blunt statement.
My husband is well-endowed and sometimes he just has to stop. Now, it's not often, mind you, but there are situations where I quit admiring his stamina and just ask "Really?" Well, I'm not that hard-assed about it, but sometimes I'm just a little sore and sound short.
And yes, the size does have a lot to do with it. I've had lovers who were nowhere near Cap's size and either I had more patience or they just didn't rub me raw.
And forget Viagra! Hoo boy, that's a whole other story. He'll get much harder and stay that way forever. Sounds like a dream come true, but let me tell you, it's not. Darling, if your diddy gets soft your tongue doesn't. Remember that! LOL!
Oh, and one last thing, I will always, and I mean always take care of him after I make him stop. That makes him stop much quicker!