Dear Watermelon,
I take photos of the bleeding I experience (which like you is occasionally squirting out of me) and did so that if anyone doubted me I could show them - and I've offered to show the photos to two doctors that I've seen (ashamed to say I have a collection of about
50 photos on my phone): the first wasn't interested in looking - the second said 'Yeah let me have a look' - and made a note of it in is notes, but was otherwise unmoved. In a weird way I found this reassuring and you may too.
Quantity-wise is tricky - I've bled to the point that it is still dripping out of me a good five minutes after the BM and to even stand up I've had to plug it with some toilet paper - but on reflection I think it's difficult to say and unlikely that I lost more than e.g., 50ML. Loads of variables I suppose.
I will say though that I've lost any reservation in documenting stuff, getting my hands dirty, or anything so even if you're capturing it 'grossly' who cares (?) - catch it and measure it - it's not going to be precise but it will give you a sketchy estimate, and as you get better put a patent on the method - I'll be the first to buy
All the best,
Will