Ups and downs are TOTALLY part of the journey! In anything!
With pole, I have some days where I really feel my music, and feel like I'm coming up with some fantastic moves (that I wish I was getting on camera, argh!), and getting everything right! And, some days... not so much. Can't get in the groove, can't find any music I like, can't even seem to do the easiest of moves. I've lost the groove and, in some of those moments, I feel like I'll never find it again.
This happens also with writing- even now. I've been writing for more than fifteen years, it's my first love, my hobby, my profession, my degree major and everything that I live to make my heart beat- and some days, I just can't frigging write at all. False starts (which are generally trashed), horrible ideas, a loss of voice, all of it. Some days I can't even type straight.
It happens to ALL of us, in ALL things! It's totally natural. Humans aren't machines, though we like to think we are. You ever suddenly breathe wrong and go into a coughing fit? Just means you had a slight malfunction! You're not perfect, and your dancing isn't always going to be perfect, either. And, that is true of EVERY human on the planet. Even the Dalai Lama.
Remembering these things, that you are going to have off days, even months, is a big part of not getting down on yourself. You're going to struggle with things.
You've had two weeks off, which is going to take you back a little bit on your strength. Just a little bit, but sometimes it's enough. And, if you're still not at 100%, that invert is going to seem a million miles away! Weakness and frustration is part of being sick, too.
Be gentle with yourself. Remember that all of us have gained, and even inexplicably lost, moves for seemingly no reason! The days we gain are ones we feel good about, and the ones we lose... well, I think we need to just accept. You don't need to place your worth, as a dancer or otherwise, on one bad day- or even one bad month.
Congratulate yourself on getting up there, and doing your best! You're on the road to your goals- no matter how difficult, slow, and bumpy that road might be.
We're all right there with you!