Back pain after egg retrieval

Hello Everyone. I just had my egg retrieval yesterday. I had 22 eggs retrieved. This is my third time doing ivf. Every time after egg retrieval I sleep sitting up for 3 days because my nurse told me to. I've been feeling pretty good after this surgery, but right now I am having stabbing pains in my mid to upper back. Has anyone else had this after egg retrieval? Do you know what could be causing it? Thank you in advance for your replies. Baby dust to all.