I am also in a similar position that you are in. I am also 29 and it was tough! I got a good job but I was having to call in sick. But I explained to my bosses that I caught some kind of bacteria and saw 10 doctors. I was being honest about
catching a bacteria and seeinging 10 doctors though. Even though I told the first 8 doctors I got Lyme disease so I was making my "medical mystery" an easy problem to solve when seeing them, they still didn't belive me. Only after I see the Lyme Literate Doctors is when a Doctor finally believed me.
At first I could not work! I would sit in my office all day long searching about Lyme disease and how I can get better. Then I would spend half the time resting in my office taking many different medications in an attempt to get better. But overtime I slowly got better, now I think I am much better and I'm actually able to do my job like I used to before which I am glad, and my bosses notice I am able to work again too.
I will say try and hang in there, just let your bosses know you have been ill but are undergoing treatment. It will take some time before you get back up to speed. But just hang in there I would say. Maybe ask for a reduced schedule if possible? Take Wednesday off might be a good suggestion? Some days I would just call in that I would be coming like 3-4 hours late, and somehow I was lucky my boss was okay with that.
You can just let them know you haven't been feeling well but are doing everything you can to get yourself well.