Professional liars such as undercover cops, may not feel guilt because they need to lie to do their job and survive. And liars who have mental health issues may not have tells because they just plain don't feel guilt or remorse.
You may think you have gained an extra special ability detect lies from your love- Because you spend so much time with them and believe their is intimacy you think you know them like no one else knows them. In fact, as intimacy increase so does your confidence in your ability to read you man. Even when part of you feel there is something wrong if someone else tells you, "He is lying", or "He is dating someone else." You may feel or say, "Oh, I know him, he would never do that."
You may have lost trust in yourself that would help you be discerning - You may also get lost in the instability of the crazy tilt and whirl. Even when you do know something is wrong, and talk to your partner and they continue to lie, to the extent you begin to lose faith in instincts and question your very honest and accurate feelings of insecurity. You can tilt back and forth between absolute trust and absolute lack of trust. You can look them in the eye and say, “I know something’s wrong.” And they can look you in the eye and say, “Darling I would never do anything to hurt you,” and lean in to kiss you and rub your back. You feel at a gut level the mismatch of love and deception being presented together. It can be intense and painful. You want to claim the love message’s truth but at some level you know something is wrong. This may swirl you into a crazy tilt and whirl of instability. Again the messages of love and the messages of a lack of love that feel like the lack of love or decent, "I love you I want you I need you, but I have to go out of town for a week and I will be out of touch." The cheater can even create this crazy tilt and whirl without malice. They may love you, but they lie because they just happen to also love and or be attracted to someone else too. Or they may create the crazy ride out of more selfish reasons, such as the desire for power, control, thrills or mental health issues such as narcissism. (Google the term Love Bombing for more information for more information on the more malicious form of this crazy making.)