The `Adrenalin Junkie` star underwent a surgical procedure to have the organ taken out on 25.03.12 and posted a photograph of himself in his hospital bed on his twitter page.
Alongside the grainy image of himself and fiancee Lisa Stelly, he wrote: "This is what you look like when you have had your appendixremoved."
The 26-year-old star - who has previously been in rehab to be treated for an addiction to painkiller Oxycontin - later joked the medication he had been given combined with the music he was listening to meant he was having "too good" a time in hospital.
He tweeted: "Man, high powered pain killers + radiohead = dangerous territory for me. I gotta get outta this hospital. This is getting to good. (sic)"
Jack and Lisa - who got engaged last September after around four months of dating - have been leading a quiet life in the lead up to her pregnancy.
Lisa tweeted last week: "Jack and I`s new hobby is going to cheese stores and buying cheese, salami, olive oils, and finishing salts. Hi, we are officially boring."