It only becomes a mental illness when it affects your life in a negative way and you neglect your responsibilities because of it. As long as you are able to manage your life and don't harm anyone, I don't see a problem.

I experienced this and it was really hard. I reached the point that my day wouldn't be complete without daydreaming about him. I think it'll just go away on its own, like what happened to me. But if it's affecting your daily life or makes you do things you shouldn't do, I suggest seeking some help.

Keep dreaming, love! It's normal & natural & you're going to be fine

It's ok to dream...