Help, trying to get my old Job Back?

I recently resigned my job with a company that I was with since 2007 due to fatigue due to standing all day and a dynamic atmosphere with the costumers. You see I'm planning on going back to get my job back after 3 months. When I resigned I gave them advance notice but I don't know what to say since they will have tought question. I mean it's the main boss that interviews you on top of that right after I quit I tried to go to unemployment benefit but I told the truth as to my condition I also made it clear as to why I was resigning due to health issues. Do you have any suggestion about how I should go about it to successfully get my job back