H.B.
Oh my goodness, I would definately think that making him go back to his room, which is obviously very scary to him right now, would make him feel even more scared and insecure. One and a half years old is not an age to teach independence or to learn not to be scared on their own. He is essentially still a baby, and needs you, and likely will for many more things for years to come. So much research is available now as to how stressful and mentally and emotionally disturbing it is for kids to cry themselves to sleep....compound that with him being scared on top of wanting you near....UGH. Please give that little boy what he needs/wants which is to be cuddled and close to you as he grows emotionally and developmentally and you will find that you will have a grown man some day that is secure, independent and trusts others to be there for him, especially his parents that he loves the most in the world. He doesn't need a teddy bear in place of a warm body to hug when he's scared or needs love....he needs you :-) Being there for him will never be a 'bad habit'.
Best wishes and remember that these stages only last such a short time, just like their childhood....stay close and you will never regret it.
And if you "honestly feel as if something is scaring him" as you stated, how do you think HE feels??? I would COMPLETELY change his room around as much as humanly possible if you refuse to have him with you in bed. Rearrange the furniture, buy new bedding, change where the night lite is, add new wall decorations, play a calm music cd at night or nap....basically make it a whole new room that will hopefully take his mind away from whatever has scared the living daylights out of him...and don't leave him alone anymore when he's scared, especially in the 'new' room and he will gradually get better...it may take time or you staying in there with him on an airmattress or something for a while till he gets his security back. He has to trust that people will be there to protect him, not to leave him alone and scared.