Spar more. 'Alive' sparring is the only true teacher.
What you could do is practice taking a short step before you kick.
Say, what stance are you usually in? Orthodox or southpaw?
Anyway, the trouble recently has been many gyms are teaching to kick without stepping in as they so count on the opponent being the one going to rush in, so you don't need to step forward while kicking. This however is wrong. Practice kicking with stepping forward every time you kick.
For example; you're in orthodox, take a step forward with your rear leg and kick with your lead leg. Another one is to step a little with your lead leg and deliver a "stronger" kick with your rear leg. Understand now?
The only weakness to this is that people who are counter-fighters, are very prone to stop-hit you while you're advancing. But don't be afraid, I believe you've got enough skills to set it up well.