help!

About a month ago whilst at work a live louse fell out of my head. ( I work with children ) I was firstly mortified and instantly went to buy a nit comb and obsessively combed my hair, I found two more lice after that. Kept combing hair but never found lice again. I ordered a fine wire comb thing for nits and lice and I have obsseivly been combing my hair everyday. I have not found anything but my head is extremely itchy and I feel like I am going crazy. I had 3 louse and now nothing yet head is extremely itchy!!!! Please help me with what I should do moving forward?