I left my husband almost 5 years ago,and left our three kids because it was the best decision for them at the time,I am in a better place now and want to know If I could get custody of my kids now,we have never been to court,and he tries to keep them away from me as much as he can,what can I do,I have always been here and have always wanted to remain in their lives,I just couldn't take them with me at the time.

Getting custody after 5 years of established status quo by your husband will be difficult. If the kids can be show to be thriving in their current environment, a judge will be very reluctant to grant you custody. It will be long, expensive and you probably will not prevail.

However, you have a good shot at getting established visitation times so that your ex cannot deny you time with them. If I were you, I would go pro se to your local court and file for visitation based upon the standard guidelines in your state.

Wendy

I agree with Wendy. A court would look at the disruption and uneccesary upheavel any change would cause to the children especially if there are no concerns regarding their welfare.
Have you spoken to your children about this?

I too agree with Wendy. File for visitation, get reconnection with your kids. Then see about custody.