When a man claims he's slept with a lot of girls, and brags, is he lying?

My boyfriend claims he has been with so many girls. It seems hes been with all the girls on his block. Then he sometimes tells me how girls flirt, and check him out. He even states these one particular girl always asks for him when mom goes to her drs appt, since shes old an he accompanies her. So the nurse asks if his married and why he didnt go. Is he bluffing??? Do men really brag if its all true??? And why tell me this things if im his girl???