A nursing diagnosis statement translated into regular English goes something like this: "I think my patient has ____(nursing diagnosis)_____ . I know this because I see/assessed/found in the chart (as evidenced by) __(defining characteristics) ________________. He has this because he has ___(related factor(s))__."
"Related to" means "caused by," not something else. In many nursing diagnoses it is perfectly acceptable to use a medical diagnosis as a causative factor. For example, "acute pain" includes as related factors "Injury agents: e.g. (which means, "for example") biological, chemical, physical, psychological."
To make a nursing diagnosis, you must be able to demonstrate at least one "defining characteristic" and related factor. Defining characteristics and related factors for all approved nursing diagnoses are found in the NANDA-I 2012-2014 (current edition). $29 paperback, $23 for your Kindle at Amazon, free 2-day delivery for students. NEVER make an error about this again---and, as a bonus, be able to defend appropriate use of medical diagnoses as related factors to your faculty. Won't they be surprised!
If you do not have the NANDA-I 2012-2014, you are cheating yourself out of the best reference for this you could have. I don't care if your faculty forgot to put it on the reading list. Get it now.
Go to NANDA-I 2012-2014. Let's look at what you have so far.
1) "Anxiety r/t financial stress, AEB pt states "I don't know how I am going to pay these bills without working", pt has had 2 anxiety attacks in the past 2 days, patients wife states "I have never seen him so nervous about money since his surgery.""
Anxiety's related factors include "change in economic status, situational crisis, threat to economic status, and threat to role status"-- say that; defining characteristics include "reports concerns due to change in life events," (there are others he may demonstrate-- look at the list) and append the statements they both make to support this. Good-- but you have to use the official language.
2) "Impaired physical mobility r/t left side below knee amputation, secondary to diabetes mellitus type 2, AEB gait changes, pt states "I don't like to walk around my room because it hurts."
Impaired physical mobility's related factors include musculoskeletal impairment, and so you say, "musculoskeletal impairment, right BKA." (It's true he has DM, but that's not why he had the amputation-- there are lots of diabetics who haven't. He had his because of the damage his peripheral vascular disease visited upon him.) You don't have to cram his whole medical history into this one diagnosis. Your defining characteristics include things like "limited ability to perform gross motor skills, gait changes, engages in substitutions for movement," so you say those (you have "gait changes" already) and add his words, and Bob's yer uncle. Good job.