Sorry to say at 3 to 4 weeks that is definitely a cockerel (little boy). Not all strains are the same, but my cockerels always feather out slower than the pullets. Between 4 and 6 weeks the comb will turn pinkish and the wattles will show if it is a boy.
I am actually delighted! I wanted two full sized Roo's - I have 26 total - but I think 4 of my OEGB's are Roo's - and I have doubts they are going to be able to be able to successfully cover my BA, Barred Rock or Gold Wyandottes. So - I am super excited. Thank you!