How do keep them little flowers out of my grass

I put the weed killer 4 times last jear & didn'tth it

Move often so they don't seed themselves or dig out when you see them.

If the flowers are purple then you have Creeping Charlie which is a vine and the tendrils root themselves. You need a weed and feed to kill the weeds and feed the lawn so it will thicken to smother the weed growth. I found that Spectracide weed and feed in the hose end sprayer works. Kills the weeds within a week and feeds the lawn. I have tried all different weed killers and this one works.

what little flowers....You have to use a weed killer for the weeds or unwanted wild flowers that kill them but not the lawn.Ortho and spectricide both offer these products