So I'm talking to an ex fiancé again and he admits to still loving me. He knows I love him and want him back. But now he won't take me back even though he loves me and makes futer plans with me. He even admitted to missing "us". Why won't he take me back?

There's a reason the two of you broke up, and love doesn't fix everything. It sounds like he knows there are still issues, and he doesn't want to deal with those issues again, since he can't fix them.

Love isn't enough. If it were, then you two would still be together.

Why did the two of you break up?

Why did the two of you break up?

He said he lost some of his feelings and didn't want to hurt me even more in the long run. But he's acting the same as he did when we first fell in love. Other than we've kind of grown up a bit since then. He texted me through out his relationship after mine when his girlfriend didn't want him talking to me. So he went behind her back to keep in contact. Yet when they break up and we can be together, he chooses to be single.

You have to assume he is single because he wants to be. He may miss you, but that does not mean he wants to be with you.
The fact that he was talking to you behind his girlfriends back is funky. Maye he is talking to someone else.
At any rate, I would stop talking to him as you still have feelings. Don't get wrapped up in him. He is not getting wrapped up in you.

Maybe you need to make the first step. Best wishes.

There are no more steps to take - you told him you want him back. Now you wait. Maybe absence will make his heart grow fonder, maybe it won't. Don't push it. If neediness was any part of the original reason for breaking up, it will be again if you get back together. I'm not assuming anything, so correct me if that's not it at all.