Ok, that's a huge question. I'm going to take a stab at one aspect of it- the aspect I think you really need to hear about and think about right now, Ann.
There are various ways to define and describe recovery, and I'm not saying this post is the end all be all way to define it. Not at all. I think at different points in treatment and recovery it's appropriate and important to focus on a variety of aspects of recovery, including, physical health, eating disordered behaviors/symptoms, mental/emotional health, quality and quantity of relationships... just to name a few.
And what "counts" as recovery can be defined a bit differently for each of those aspects (as well as defined differently by different people).
Ann, where you are in recovery doesn't need to be defined by your medical health (as far as I can tell, and as far as you allude to- you seem to be in good medical health- if I'm wrong about that, please address that right away). And your eating disorder behaviors/symptoms are really quite calm, which is so fabulous.
So, what counts as recovery for where you are?
Here's what I think, and others can add in too... I think recovery for you at this point is about a state of being, a state of mind, a state of connection to yourself and the world around you. I know, that probably sounds vague and maybe even silly. But I really mean it.
Ok, so 17 weeks is a really long time to not binge/purge. A really long time, and that's great. I don't think the process of your recovery stops or even slows even a bit because of a purge. I see you as continuing to steam right ahead- as long as you can do a couple of things here.
First, accept that things like this happen and don't get all perfectionistic about it. Or judgmental. Second, see it as an opportunity to look at how far you've come in your work on yourself, how hard you've worked, and how much all that work has paid off. Think about how strong your work on yourself is- how enduring. How it's really standing the test of time, because it is. Third, use the purge as an opportunity to fine tune your work on yourself. It's a great time to pose some questions: are you paying all the right kinds of attention to yourself that you need to be? are you taking good enough care of yourself? did you let something slip by (like not acknowledging an emotion, or not dealing with a stressor...) that you need to address? Last, don't get all rigid, don't let yourself slip into that thought of "oh no, now I have to 'start all over again'" and don't retaliate against yourself or try to somehow "compensate" for "screwing up." Just keep going with exactly what you've been doing (and ask a bunch of questions so you can make any minor adjustments here- and they are minor- there's no heavy lifting you need to do as far as I can see- just a little tinkering here and there maybe).
The moral here is that you remain "in recovery" and that didn't change because of a binge and purge. Don't let yourself get trapped in your head and a wacky thought process here. Just go right on doing what you know you need to be doing... (I actually thing that's a pretty darn good definition of what recovery looks like: when someone just keeps going on doing what he/she knows she needs to be doing, with her eye on the big picture, and doesn't get derailed by details that don't need to derail her).