The overall making up stories (when you know they are obviously false) may be part of a vivid imagination, vivid dreams, trying to get attention, maybe trying to get someone in trouble (such as a kid in school that bothers her) I think some kind of counseling would be helpful, if only to enhance communication and help you understand her intentions and reasons for certain stories and for her to learn that she should not make up stories like that; she may not be believed if it really happens in the future. Now to the specific part of you bf touching her: Did you ask him about it? Here is the thing, she might be right! But not in the way you may assume. She may have had an accident and he helped her get cleaned up and changed? Maybe she took a bath and he helped her dry off, I can see an innocent 'touch' happen there. nothing sexual, just part of parenting or taking care of a younger child. I don't know how involved your bf is in parenting her, but even with a 5 year old there can be occasions where the touching of the genitals is kind of part of the job (such as helping with cleaning or drying off). The thing with the boy at daycare is a bit different. It may have been an incident of natural childhood curiousity in an unsupervised moment. I do not mean to downplay your fears, I think in this day and age they are the right reaction. Yet at the same time we have become programmed to think of the worst first. I hope you can find some clarity through conversations with your daughter, your bf, and together with your daughter with a counselor.
Instead of finding if the story is true or false you should concentrate on helping your daughter. Something is going on with her if she is lying and even if not someone has tried to manipulate her. She's five not 15/25 to play games. Here it seems to me you're more concerned about the other aspects of your own life than your daughters well being. You haven't even tried talking to her with clear concise questions or asking if she's indeed telling the truth. I would suggest you both see a psychologist together. Try to get to the bottom of this and not worry about CPS cause they know what they're doing.
If you are finding that the story is false, simply share with the CPS what you are finding. They will probably be glad to close the file, they have too much to do already.