I currently work front desk in an office (my full time job), I plan people's vacations, and I work in a science museum very part time (love this job). I was recently told at my full time job that they're worried I'm not a good fit because I have a hard time getting tasks done by a deadline, I can't keep up with the pace, and I'm not good at multitasking. Personally I'm better when I can focus on one task at a time but I need this job so I am trying my best to keep up and improve.

I'm going as far as to see if I have something going on in my head that affects my work ability (possibly ADD). I was diagnosed with anxiety as a child but no treatment was ever pursued as my parents didn't want me on meds. Reading up on it now I also feel I may have had ADD since childhood, my parents have even said the doctor probably would have diagnosed me with it had they looked more into it in my childhood but again didn't want me medicated. I have trouble staying on task, my mind wanders often, I'm constantly late to places when I shouldn't be, I get impatient in conversation and just bust into it, and when I try to listen to someone my mind drifts as well after a period of time.

I'm not really sure what to do. Is this job workable given I find out what's wrong with me, is something else more suitable? I am trying my best to keep up at work.
I'm not really sure what to do or where to turn. My husband of course is stressed and long story short won't be able to deal with the situation if I lose my job. I just needed to type this out somewhere and maybe get some guidance. I'm sorry that was long!