Did not get pregnant again.i am buying clearblue fertility monitor..will it help?

:( Crying quietly all evening..do not want hubby to know i am this sad. have been TTC for 3 months now . My periods are irregular so i count on OPKs and CM. We had BD the night before i got positive OPK , then the afternoon next day and 2 days after. My hubby loves kids and is favorite uncle in all close friends and families.. i want to give him his own..:(