having sex is probably the best way to tell. when someone no longer loves you, it'll feel more like you are violating their body than making love to them. needless to say, they'll probably be more reluctant and or nervous when you signal them you want it...lols..if they are cheating, they might have some serious temper issues when you want it...it's the guilt they feel...I speak both from experience and observance of others..lols