Why is my basil wilting?

I have it in a container by my kitchen window. I repotted it after buying it from the garden centre a few weeks ago and initially it was doing well. I have been pinching leaves from the top and I have not allowed the soil to dry out. The soil is still moist at the moment so I cannot rewater - however the basil leaves are still wilting. I have also used miracle grow plant food in the potting mix. What can I do to remedy the problem? Or what if anything have I done wrong?