The best thing is to take things easy, take into account the small details and attentions he has with you; perhaps they say more than words and you haven't noticed.
For self-protection: Past relationships are likely to have left your partner with a bad taste in his mouth.
The experiences have not been so pleasing that they left as a result the generation of an invisible shield to take care of themselves. What for? not to be hurt again, because they feel vulnerable. So perhaps for this reason avoid repeating the phrase often.
Fear of commitment: There is not much to explain saying these words can make the person tied dislike the idea of raising the level in the relationship. Perhaps he said it once, but repeating it often, unconsciously, increases the level of commitment in a relationship.
It is safe to say that you walk "with lead feet" and prefer to keep the ones you love to limit the ones you love for very special occasions, or definitely avoid them.
They're not sure they're sorry. It doesn't take everyone the same amount of time to make their feelings clear and they don't say it until they're sure they're sorry.
In this case take into account every detail, their attention to you. There are other ways to know if he loves you even if he doesn't tell you.
The word is not familiar. Maybe he grew up in an unloving environment where affection and love phrases were uncommon. Remember that the way we see mom and dad showing off their physical and verbal love influences our affective relationships.
The fact that they had not shown their affection in front of their children or towards them, makes it difficult in adulthood to express themselves, because they simply did not show them how to do it. It's probably just that it's hard for him.
Doesn't he really love you anymore?Probably it is happening that their feelings have changed, you should take into account that in relationships this is very natural.
If, in addition to the absence of the sentence, you have noticed that his behavior with you has changed and you feel a total inattention in all aspects, it is time to speak it clearly and face to face.
Don't wait any longer; maybe it's still time for both of you to act and detect because the feeling is changing.
Maybe they're just going through a bump, think of fun activities they could do to rekindle love: a romantic dinner, a walk in the woods, a getaway to a hotel in another city, or definitely a vacation together to get the most out of it.