The 29-year-old reality TV star needed proof of the husband's alleged infidelity due to a clause in their prenuptial agreement and got someone to trace his movements.
Lamar - who is allegedly a regular user of crack cocaine - has been accused of having affairs with Polina Polonsky, Jennifer Richards and another three unnamed women.
A source told RadarOnline.com: ''Khloe has not only photographic proof that Lamar cheated on her with at least five different women, but has copies of text messages between Lamar and the other women.
''She is a very smart woman and knew she had to get the proof because of the infidelity clause in their prenup.''
Khloe and Lamar - who wed in 2009 - are reportedly living separately after she kicked him out of their Los Angeles home for cheating on her.
Lamar's mistress Polina claimed he lived with her for six weeks in June and July during which time she also witnessed him using crack cocaine.
Spencer Morrill believed he was in a relationship with the singer and that she was hiding messages for him in her songs.
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Roberts had left the band in 2012, due to problems with blood circulation and other health issues.
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