Why Am I Not Conceiving After 2 Years, With My Husband S Low Sperm Motility And An Echogenic Focus In My Endometrial Cavity?

Hi, I have reqular cycles but I did not conceived for 2 years of trying..we had reqular tests done..my husband sperm health is little poor..20 million and sluggish sperm 55% But doctor gave me letrozole for 3 months still I did not concieved..I have a small econgeni. Focus of 4mm in endometrial cavity..what is the problem