well, you know it could have something to do with it. the truth is, i don't know. perhaps if you went down to 25% fat or 30% fat, it would be different, you know? it could be that your tipping point is 32.5691132% fat, and that if you just had 32%, you'd be ok, you know?
it could also be any number of other factors--such as any other aspects of the diet that changed such as having more soy than before (which can decrease period symptoms for some women by increasing estrogen in the body) or having less soy than before (which means that your body does well with soy and it isn't a big factor for you). there could be other thyroid situations that you're nto sure of yet, and a diet can affect that. Iodine loss might be a part of it, for example, which can happen at diet switches.
could be a lot of things. I think it's a good idea to observe it.
also, in the coming weeks i'm working on a thyroid and reproductive balancing workshop for my clients. i'm going to have some papers about it, and i'll let you know when i have it. there are some great movements for "toning the uterus" taht seem to decrease pms and related symptoms.
oh, and caffine can have an effect (too much or too little).