Yeah, you move around a bit. Depending on your seat, bike, butt, arm reach, trip distance and how tired you are--you may sit differently.
I noticed on my CBR how the seat slanted forward, dumping me forward onto the tank. A much more experienced friend told me "it would go away once I began to ride faster". It did and it didn't. I would certainly consider changing the shape of my saddle if I knew I could do a decent job of recovering it.
It will take a bit of time, but you'll figure it out.