You can get the following tests done just to rule out any treatable cause: CBC, T3, T4,
TSH, Serum
B12, Serum Vitamin D3
You are probably stressed out and worried.
There are a lot of things that you might be wanting to do, but you may be so worried that you will not do it correctly, that you are afraid of starting out in the first place.
You are not alone. It tends to happen because we want everything to be done properly.
One suggestion that might help you is: whatever work you have in mind, just start with one of them today. Do it for just 5 mins or 10 mins. It does not matter if you don't do it perfectly. Just start. Once you do it, you will automatically get the confidence and the drive to do it.
Also try and reduce the things you have to do in a day. Just list out 1 or 2 things that you have to do in a day. Those are your most important tasks and you have to do that. Many times we make these big lists of everything that we want to do and then we get so overwhelmed that we aren't able to do anything. So just write down 1 or 2 things that you have to do in a day.
Remember that you have come a long way in life. You can do this.
Next Steps
You can try out meditation. There are a lot of apps available on Playstore and ioS that teach meditation. It will help you focus better. If not meditation then any activity that you enjoy doing will help you build your focus if you do it on a daily basis - reading / playing a sport / drawing etc. You can also try maintaining a journal or diary where you write down all your thoughts.
Also remember to take time out for yourself just to relax and heal. We all need a break.