My V is very tight what can I do?

If it's sudden, I'd see a doctor. There might be something going on with the muscles, or you could be having an allergic reaction to something. Too much sex would cause your muscles to be looser, not tighter, though if you've used a condom with spermicide or a new kind of condom, you might be allergic. Try using dilators (basically sex toys that go up in size) if the problem persists to stretch the tissue out.