Do you mean, what is the difference between "I love you" and "I am loving you"?
First, let's move it down one notch on the emotion scale, and change love to like, just for this example (because otherwise we can get into discussions of "making love" which is not the point, I don't think).
I like you vs I am liking you.
When we speak of emotions such as love, like, hate, dislike, they are thought of as permanent, inate feelings. You can't turn them on and off, start and stop. So, the concept of present progressive "am liking" doesn't make sense, in most contexts.
You can say I walk, or I am walking, because these are actions that start and stop. I walk to the store, suggests it is my habit to walk, rather than drive; I am walking to the store, suggests that at this moment I am walking there.
It is possible to say "I am liking ... " in the right context. Perhaps you are listening to a political candidate, and he actually starts to make sense, to appeal to you. You might say to your friend, "I am liking what I am hearing." It suggests you are just getting there, to liking it, not quite convinced but well on your way.
The concept doesn't work with love. With love, as you know, you are hit all at once and it is forever!