What Causes Pain In Shoulder And Under Rib After Appendix Removal Surgery?

Hi I had keyhole surgery to remove my appendix 4 wks ago. My appendix ruptured so I also needed to have 2 collections in my stomach drained out. I was in hospital 2 wks. Since I have got out Ive had bad pain in my right shoulder Its like a stitch and over the last week Im getting pain under my right rib it feels like there is air stuck there. Any Ideas?