Every body is different, but in general, when you are sitting, your vagina ‘sits’ with you. What I mean is that there is a bend in the vagina that would indeed make having a dilator inside of you feel uncomfortable. The ideal positioning would be lying back, you can slightly elevate your hips with a pillow. And while you are doing that you can focus on relaxing the muscles that you have voluntary control over. Use the time to relax and take some deep breaths. Hope that helps!