Kegals really do help because you can squeeze him and it feels good for both of you.
Anyway, a long penis (and that sure is one) might make the cervix sore if it hits it or cause bruising. It won't permanently damage you, but you might get sore.
Try positions with less penetration. For example, with him on top, close your legs under him so your knees are touching. It will keep him shallow and keep contact and friction high. Or spoon, that keeps it pretty shallow. Or you on top, with you controlling the depth of penetration. I'd just play around and see what feels good!
I recommended this to someone else but I can't remember who. They have vibrating c*ck rings that can be placed on the base of the penis. They are rubber (like silicone or something soft) somewhat wide (about an inch or 2), so the base of his penis would be stimulated by the vibration and he would stay more shallow (or he has to because there's a ring there) plus the vibration would stimulate your clit. You can find them online anywhere sex toys are sold.
I hope that helped....