As for the tight foreskin, you don't need to get circumsized to clear up that problem. And yes, I do think it is a problem. When you're erect your foreskin should either already be retracted past the head, or you should be able to do it manually with no pain. If you can't retract it that far you're going to get all sorts of gunk building up in there. What you probably have is called phimosis.
I had the same problem, and got it checked out. The doctor prescribed me a cream to put on a few times per day and to keep gently retracting it and the skin will stretch. After a few weeks you'll have no problems. Go to a doctor for a quick, five minute check up and it'll be smooth sailing.
Since you didn't mention ejaculating during sex I take it you're either not having sex or this problem is only related to masturbation. If it's the former then if you don't do anything about your tight foreskin it might rip when it's pulled back if you're thrusting in and out while having sex, and that would be very painful.
And finally, if it's because this only happens during masturbation, and not during sex, then it sounds to me like you do it too often and, like anything repetitive, it's probably just getting a little dull. Your senses might be dulled because of the strength of your grip (nowhere near as soft as a vagina!), so the pleasure just isn't as big as when you were younger.
My advice is exactly the same as the advice someone else on these boards gave me a long time ago when I posted one of my very first posts, which, believe it or not, was almost the exact question you've asked: quit masturbating for a few weeks and regain you sensitivity (don't worry, it comes back, it's not lost!), use a looser grip and, if you have a partner, play with them more than with yourself
