The former Bradford star, who's form has been electrifying since his switch to Hillsborough, injured his leg against Colchester last month.
Then when he recovered from the minor knock, the 26-year-old then contracted chicken pox which can be potentially very harmful in the later stages of life.
Now Johnson is hoping he can catch up on his fitness before the end of the regular season next week although admits Wednesdayites may not see the best of him until the start of the 2007/08 campaign.
He told Footymad: "The last few weeks haven't been good for me. I came to the Coventry game feeling really tired but now I am back and just have to focus on my fitness so I can get back playing regularly again.
"Getting chicken pox is wicked. I felt like I was dying for a few days but I am well again now and just want to get back in the team. I am not really fully fit yet but like I said, that's something I have to work on in the next few days and hopefully everything will come back.
"I am really enjoying myself here and I want to keep working hard to play well next season and do well for the gaffer. Next season I will be a lot fitter so it will be much easier for me to play."
So far, JJ has only started four games for The Owls and made a substitute appearance at the weekend against Coventry but he has many happy memories from his Hillsborough career so far.
He added: "The club here is massive; I knew that before I came. My highlight so far came up at Leeds when I got my first goal, that was really brilliant and I also enjoyed myself on my debut at Luton despite not getting a great result."