I feel like I should weigh in here.
I have been dancing for 6 years now, and can barely do a basic invert. I spend hugely long hours trying to conquer one move, and not just because of a lack of strength or misunderstanding as to how my body works (which are both factors, let me assure you), but because of fear.
Fear means that I would rather completely avoid the inverted crucifix because it makes me afraid of falling, and of being upside down. Fear means that I don't want to push myself too hard, because I've been injured. Fear means that I don't trust my body when it comes to elbow/hand/head stands.
Now, I'm not saying that this is your issue. What I AM saying is that everyone has their challenges! Some people can invert within six weeks of starting their pole dancing, but can't figure out how to do a carousel spin. Some people can do a knee hold without feeling pain, but can't seem to invert for the life of them. Some people get tricks like they're nothing, but can't make an actual dance out of them, or connect to music.
Your progress is YOUR progress. It's all yours, and you fought hard for it. You worked for it. You made your progress real.
Getting it slower than someone else doesn't mean it is worth less. It doesn't mean you worked less than anyone else, or you slacked off somehow.
The idea of "should have this move in ___ time" is comparing your progress to someone else, and you need to know: Your progress is INCOMPARABLE to anyone else's! Your progress is all yours, and you learned things that perhaps someone else didn't.
Which also means that maybe you have something else to learn within these moves that other people do not. If you keep trying, you'll figure it out. This is the nature of humans.
I will also say this: Tell yourself you're awesome, and that you WILL learn the things you don't know yet. Instead of "I'm horrible at dancing," or "Maybe it's my size," what about "I will learn how to dance!" or "My size is what it is, and I can already do amazing moves!"
You ladies are doing great, and don't you forget it! Just by taking on the challenge, looking at something and saying "Yes, I will learn to do that!" you've taken a massive step forward. By continuing in the face of challenge, and of disappointment and perhaps frustration, you're showing just how amazing and willful you are.