Yes you can use organic skim milk but non-dairy is recommended for best results, especially when you are first starting out. Many women with PMDD are lactose intolerant and/or sensitive to the casein protein in dairy which tends to be a problem in the luteal phase when the intestines become more permeable due to high hormone levels. You can always add organic dairy back in the follicular phase and look for GI responses like gas. If you have lots of gas with dairy you most likely are lactose intolerant and therefore should avoid dairy for better menstrual and ovary health. Undigested lactose can cause problems for the ovaries.
see these research studies
If you have any underlying autoimmune condition the undigested dairy or gluten proteins (peptides) can also be a problem because we understand the gut is considerably more permeable with inflammation.
See this study by Dr. Fasano
Is there any autoimmune diseases or syndromes in your family history? Have you been diagnosed with IBS, IBD, Endometriosis, PCOS, fibromyalgia? You can look at this list for
the top 64 autoimmune diseases