Seeing you are mid cycle are you sure it's not O pain? Even if you don't normally get it, you can suddenly just start getting it each cycle. It's usually only on one side that you feel it though but some women are quite uncomfortable for days after O.

As for the ferning - you will normally get two surges of estrogen (sometimes more) in a cycle which can produce ferning - mid cycle til you O, then it will start to disappear and then then you may see it again just before you get your AF. So if the ferning has disappeared & you are mid cycle then it was probably caused by O.

You can also get ferning when pregnant but usually this wouldn't show until about 3 weeks when implantation has already happened and your hormones get going. I would imagine it would be quite strong too as your estrogen levels would be higher than ever.

Like BW I've only ever had symptoms from 3 weeks onwards. With my pregnancies I've only ever had cramping around when AF would have been due.