Not insane at all!
LDRs are tough. I don't know anyone who has gone through a prolonged LDR to be able to sail through it easily without any tough spots. Heck, I've known couples where one of them had to go on a business trip for 1 or 2 weeks, and it was hard on one or both of them - just for 1 or 2 weeks!
Agreed with CMG. Sometimes, the feelings do kind of just pop up out of nowhere - I've experienced that myself. My fiance says that I seem to have cycles. I get nervous/clingy/insecure immediately after parting ways, then I cheer up for a little bit, then I get afraid again usually halfway between our apart times, then I cheer up, and then I get nervous again right before a visit. Even when we're together at first, I'll have an "attack" as we call them (what if he doesn't like me anymore, now that he's seen me after x months!). And even though I know rationally and logically that everything is okay, I still can't help but feel these feelings, and most of the time, they're like roller coasters - high one day, then low another.
When it happens to me, my fiance has me talk it out and put everything in words. And when he hears it, he can diffuse my feelings by talking to me and going through my fears one by one and talking me through them and essentially, debunking them.
If you can, try to talk to your fiance about them. Who knows - he might be feeling the same exact way! My fiance sometimes also has scared insecure moments, but he tries to be strong about them. I've found that I also feel better if he talks about them to me when he feels ready. I feel more "normal" knowing that he feels that way on occasion too (it's not just me!), and I think it strengthens our relationship knowing that we do worry about the other when we're apart - even if the worries are silly in hindsight. It shows we both still care.
It's only 7 days; I bet when you're together again, you'll feel right at home again! Good luck!