Thank you everyone for being so kind. @Nypie yes it does suck balls indeed! (I looked into vitex but I think can mess with your cycles so holding off on that for now. I started b6 last cycle but didn't seem to have effect so might need longer.)
@SarahShorty You put it very eloquently! For me it was about the potential, and especially if it could have potentially been a viable pregnancy if not for my issues. It's hard to say whether it was a chemical or not as I didn't test - but this period is distinctly more crampy and heavy than usual and just feels different. Maybe I'm reading too much into it, but I know my body and something just felt off this month.
I spoke to OH about his clump of cells comment, and I get that he was trying not to get attached to protect himself, but I explained to him what it feels like from my point of view. Of course he can only get it up to a point, but he listened and apologised and realised that he got it wrong. I literally just needed some sympathy and for him to be there, but he was trying to rationalise the situation away (he's a scientist and has a habit of responding logically rather then emotionally, but he's working on it).
So I spoke to the GP and was actually very pleasantly surprised. They agreed the sudden dramatic change in my cycles (from 34-36 days down to 27/28) and teh recurrently short luteal phase are causes for concern so they've ordered some blood tests, to be taken between days 5-7 of my cycle. Bit confused as would have thought the progesterone would need to be tested in my luteal phase, but it's a great starting point and I guess I can request that later. He even suggested that they test my OH's sperm too! Which is a real bonus, and given the variocele, very welcome.
In the meantime I'm going to continue on the vitamin b6 and continue taking 2 rest days from exercise. And also practice managing stress (wedding is 5 weeks away so easier said than done, but I'm on holiday next week - first time abroad since 2019!)
Really hoping that this luteal phase thing can be fixed.