Deciding what needs to be cited in the IA

[AdamZ333]

I've been generally panicking about things I've noticed in my IA (which has already been submitted  ). I just noticed that I forgot to include an in-text citation for where I got my method from. I used Kjheldahl's method for analysing proteins, and while I gave credit to Johan Kjheldahl for making the method, I didn't state the source I found this information from in the body of text (it's in the works cited though). I also have several instances of using knowledge from the syllabus without citing it. Should I have cited my textbook? I need to put my mind at ease because I'm really worried it could be deemed academic malpractice. Does the severity of infringement decide the punishment? I didn't copy and paste anything, and I'm quite sure my turnitin percentage is quite low, so could the punishment be less severe? i.e I get a 0 for the IA, but can still be eligible for diploma.  

Sorry for the long post! I can feel my life shortening with every IB panic attack, so I tend to ramble.