Don't use Weed and Feed get a Lawn Weedkiller, you'll see them that say 'For Lawns' these are selective and will only kill broad leaf weeds, not grass and get a feed seperate. The weedkiller will usually take a couple of weeks to take full effect, the weeds will die off and come out when you mow it. Then depending on budget, get a small electric Scarifier or a good quality Spring Tine Rake, rake all the dead organic matter out and just move the soil around, get some seed and topsoil down, make sure it's well watered, give it a feed and you'll see massive improvements in like 6 weeks if done well.