"Last week I increased my Boron intake to 15-18 mg per day. This week has been bad for me."
Sounds like Herximer reaction. But as for the blood in stool, not a good thing if it goes on long term, could mean a few things. I'd stop everything for a 5 days and try to eat more fruits than usual and see of you cant' get that blood to stop. If it don't stop, I'd say get it checked.
I suggest to get a home pregnancy test and use your first urine in the morning and report back if you choose, the result. Pls don't ask why.