Originally Posted by kingofmice
There's just that fear that since he loves her (their relationship is very comfortable) he can't possibly love me. I realize how green this makes me sound.
It makes sense, because that's what we're raised to believe, that's what we're shown everywhere, and it IS the way some people work. Possibly including you, in which case it would be even harder to wrap your mind about his working differently.
In cases like that, I think you need to look at the way he treats you, and see for yourself. You can usually tell when someone cares about you by the way they act with you, whether they have another partner or not. I think for polyamory to work, you need to be able to be comforted by your relationship with him regardless of outside relationship, seeing it as its own thing without constantly trying to compare or wonder if he does this or that with her too, for instance.
It's not unreasonable to try and set date times. If you want, for instance, a regular date night that would work around all of your schedules, it makes sense to get together, say how much you'd like to see him ideally, and then work around what's realistic depending on how much she wants to see him as well. It might really help having a regular pattern if your lives allow for it, since this way you don't have to check with everyone every time one of you is free (for instance, if you're free, you need to check that he's free too, but also that she wasn't planning to see him already. While with a regular schedule, you don't have that worry as much).
Dates with the three of you together sound like a good idea so you can get to know each other. For you, she's the established relationship and therefore a bit "scary" because of their history together, but for all you know, for her you are that shiny new person and you might seem threatening too. It should be good for both of you to see each other as individual and therefore worry less, as people tend to worry more about the unknown.
As for relationship hierarchy, different people act in different ways, and you should feel free to ask about that. It might be hard to ask "so, do I always come after her, or...?" but maybe you can find a way to ask that won't make you as nervous. Maybe you can start by asking what you should expect from the relationship or something? He seems to be willing to listen to your concerns, so talking about them shouldn't be too big a problem.