Relapse?*

First, the good news: S and I are going to stay together when he leaves. I told him that I wasn't going to wait around until he got back to see if his feelings had changed (because I highly doubt mine will) or if he had found someone else (because, again, I highly doubt I will). I said that there was no "break" or "open" about our relationship, it's a relationship or it isn't; and when he leaves, we're either together or not together, simple as that. It took a lot of courage to get all that out, but I eventually did. One thing he was worried about was what if he wanted sex while he was gone. Compromise: he gets two free fucks before I get mad at him, and the same goes for me (but I highly doubt I'll use them [I know I sound like a broken record]).

Now the unsettling news: I think I might be relapsing. I'm not sure though, which, I know, is odd. Shouldn't I know if it's a relapse or not? Well, I don't. Maybe it is and I'm just in denial. In my last post, I said that I've been more lenient with my eating. I've been so lenient that for the past week I've been over my cals, and I've been over-eating junk-food. I justify the junk-food with the thought that I still have weight to gain, I'm still "too skinny."
Last night after dinner, I shoveled spoonfuls of soy nut butter into my mouth with the repeating soundtrack of "I'm still too skinny." About an hour and a half later, I went back into the kitchen for my night-time snack. I was going to have a couple pieces of toast (as per the meal plan), but I had the absurd thought of "no, that will be too difficult to purge back up," and I went with a container of greek yogurt instead. Immediately after I finished the yogurt, I rushed to get into the shower so I could purge. I didn't feel guilty about the gobs of soy nut butter or the yogurt; I just wanted to purge.
This reminds me of when I first started purging in the eighth grade. My thoughts were, "I don't really binge, and I only purge every once in a while, so there isn't a problem." But, it did spin out of control eventually (11th grade). I feel so adamant that there isn't a problem, but there's another layer that thinks it's just like eighth grade again.
Is this is a relapse? Will it be a problem? What should I do???