delayed ovulation??

So I have been tracking my ovulation and period on this app trying to have baby #2 for four months now and I haven't gotten pregnant my son is only 7 months old but we want them close in age then we'll be done... I was wondering if maybe I have delayed ovulation? I know I may sound silly but is it possible to have delayed ovulation?? help please! I want to be pregnant by next month so our babies are 1.5 years or less apart!