A first step is to try using a lubricant as soon as sex play begins. You'll find a decent selection at your local drug store, and a more substantial one at sex shops or online. I like lubricants that are silicon-based because they are super slippery and they don't wear out easily. Water-based ones might feel more natural but they dry up quicker. I recommend trying different ones to see which you prefer.
Another option is topical estrogen: You apply the prescription cream to your vagina and it plumps up the tissues to premenopausal levels. There's also a topical estrogen product that comes in a ring form; it's inserted into the vagina and secretes tiny amounts of estrogen that does its magic. Both of these options have side effects, so you need to talk to your gynecologist before deciding if these are right for you. You also should make sure to rule out any other kind of medical issue, such as vaginal infection.
The good news is almost all pain can be solved. Make solving this problem a priority, and chances are extremely good that you'll happily reclaim your sex life and not experience it as a variety of torture!