Soy side effects?

[mybabydreams]

Hi ladies! I finished taking soy isoflavones for the first time 6 days ago and had no side effects whilst taking them. I have woken up this morning feeling slightly crampy and with sore nips! Im just wondering if anybody knows if either of these can be soy related. Ive done an OPK and there is a second line, but definitely not positive yet. I would be VERY surprised if it was in fact O related, as I am only on CD 12 and I usually dont O til well into the 30s!
I was wondering if it was to do with estrogen, which I know soy supresses.
Many thanks xxx