Omar Mateen: Strong Signs He Was Gay ... According to Ex-Wife

Omar Mateen's ex-wife is dancing around the subject, but her fiance says it flat out -- all the signs pointed to Mateen being gay ... or at least struggling with the fact he was gay.

Amid reports the Orlando mass murderer had been to Pulse nightclub multiple times ... Sitora Yusufiy and her current fiance, Marco Dias, were asked by a Brazilian reporter if Mateen was gay. Dias said Sitora believed Omar had "homosexual tendencies."

Dias also said Sitora told him she witnessed Mateen's father calling him gay several times.

Dias claims the FBI told Sitora to keep mum about Mateen's homosexuality in interviews with "American media" -- which might explain her Monday night appearance on CNN. Sitora said when she and Mateen married in 2009 he "confessed to me about his past ... and he very much enjoyed going to clubs."

She also says there were "pictures of him" -- but paused dramatically when asked if he was gay. Check it out ...