Claiming C:
《あれ『を』やる『と』ぐーん『と』元気『が』出るんだ》
《オレ『は』いっつも調子『が』悪い『と』近く『の』診察所『で』打ってもらってんだ》
@Jonapedia
I googled のだ again…:
analysis
No da or no desu after a verb, i adjective, or na is often used to emphasize the previous statement.
So you were right, it is also used for emphasis. I’m using “also” because “to want/give a reason” and “put emphasis” are ultimately to disparate functions of the structure.
Another usage of no is in the phrase XXX no da, meaning “you should XXX”. This is used both in positive (iku n da!, “You should go”, or just “Go!”), and in the negative (fuzakeru n ja nai!, “you shouldn’t joke around”, or just “stop joking around!”). This no is used very commonly in speech, and is very often said as n.
In the case if my sentence, how can I tell if んだ is:
㊀ reason
㊁ emphasis
㊂ you should do something
I don’t understand.
Another thing I wanted to tackle is もらう as in もらって in my sentence. I’ve come across it a few times and in my head it means “something about receiving” so I want to dig in and clarify this concept a bit.
patient
doctor
Speaker 
→ 
Hearer
The patient is speaking to the doctor in this case. He, therefore, is person who “receives” something from the doctor:
[] ← 