What if I want to go for full custody how hard is that and will I loose all child support

The word "custody" has no meaning whatsoever in Colorado law, so you will need to let us know what you mean by "full custody." If you mean either a situation where you are changing the parent which whom the child lives most of the time, or of you mean changing things so that the father never sees the child, then that is extremely hard. You need to sit down with an experienced family law attorney, show that attorney the current parental responsibilities and child support orders, and explain what changes you want to make and why you think they would be appropriate. There are too many factors involved to diagnose this situation with a paragraph's worth of information.