As a pilates teacher I really love helping people move on in their health and physical fitness. Usually, after every class I teach I'm asked the following question by someone with a look of panic on their face:
Does this get easier at any point?
Well there's good and bad news...shall we start with the good news?
It does. Genuinely, your first few classes are always the hardest. As your core is strengthened you'll be able to do more and the ache (well, some of it), will reduce. Promise. The best thing to do is pace yourself during your first few sessions of pilates, don't be a superhero and realise that core strength is a distance race and not a sprint.
Well, that's the good news. The bad news? There's always a pain barrier.
The great thing about pilates is that it's an incremental practice. By that I mean that there are always levels beyond where you currently are. Within exercises you can adapt posture to increase or decrease the physical stress. As you improve you get stronger and you can access all the more advanced positions. Basically, you'll always feel a burn.
But guess what, that's a good thing.
With pilates you should never be settling. Your core can be amazingly strong, and any improvements there will impact your entire body. It will aid you in playing other sports, for general physical health, for posture and preventing injuries.