Basically, it took me 27 months to get my period back after my first child. I lost a lot of weight breastfeeding and was somewhat underweight when I got pregnant again, but had a miscarriage at almost 10 weeks. I finally got pg with #2 and she's 1.5 now. They're 5 years apart. I really want a couple more kids, but I can't space them all 5 years apart. My second child doesn't nurse quite as much as my first did and when she was about 14 months I started cramping and spotted a little, but now at almost 19 months, still nothing. My mw suspects the amenorrhea could be related to being slightly underweight and not the breastfeeding. I'm mostly vegan and a dance teacher, but I do eat all I want and I only teach 4 hours a week. I recently tried adding dairy back in as I've ready that helps, but so far I don't think I've gained any weight and I've been getting stones in my cheek (yes, there is such a thing and I think it is related to when I ingest high levels of calcium? It happens when I take calcium supplements, too) so I'm not sure dairy is going to work for me.
Any thoughts on where to start? Oh, and they tested my thyroid a couple months ago and my TSH levels were fine.
The hormones you need to be fertile are fat soluble, and from what I have read, there's evidence that you may need even more body fat to restart your fertility while breastfeeding, that breastfeeding raises the threshold. It is not necessarily dairy per se that has been correlated with an increase in fertility, but milk fat: cream, butter, ghee, etc. If you are drinking reduced-fat milk, it's not likely to help, and if you are not able to handle all the calcium from whole milk, then you may decided to switch to a more concentrated form of milk fat. Milk fat also contains fat soluble vitamins (especially if it is grass-fed) that are very important for fertility.
Additionally, it might help to see what other healthy fats you can get into your diet. Do you use a lot of coconut oil, olive oil, avocados, nuts, cold-pressed flax oil, sesame oil, chia seeds, etc? These may help with getting enough calories and supplying your body with the fats that it needs for fertility.
How's your Vitamin D? A lot of us are deficient. If you're trying to get it from the sun, you've really got to be outside for a lot of the middle of the day, and in many areas, you can't make enough for a good portion of the year. The angle of the sun matters, your skin color matters, and you need a decent amount of dietary fat and cholesterol to make enough. The vegan sources of Vitamin D are Vitamin D2, which the body is not able to use as easily. Vitamin D3, what your body uses, can only come from the sun or from animal-based products. There are some lanolin-based (vegetarian but not vegan) D3 supplements out there.
I haven't had my vitamin D tested in a while, but I'm on a good D3 from lanolin and my levels were great last I tested (using this same supplement). Good point on the milk fat. Is it specifically milk fat only or is it having enough dietary fat in general? I have been taking DHA and flax oil, using coconut oil and olive oil in cooking, coconut milk and chia seeds. So I'm trying to have all my bases covered in consuming enough fat. It's funny, I never even thought of it being a body fat issue, but just remembered I was having some cramping and signs that my cycles were coming back in the fall around 14 months, but then nursing a toddler and being sick a few times took some weight off me and the signs disappeared.
I do know that milk fat has been specifically studied in reference to fertility, and I know that a number of fatty acids are very important when it comes to fertility. What I'm not sure on is what exactly it is (likely multiple factors) about milk fat that increases fertility and if there is a vegan way of replacing all the factors. There are multiple ways of getting a lot of nutrients, but I couldn't tell you exactly what you could do to replicate the fertility-enhancing effects of milk fat.