Kitten - Health problems

My kitten is just over 4 months old. I got her just over a week ago - she
wasn't entirely healthy then - was still sneezing and coughing (from the
kennel flu), but on the way to recovery. She finally stopped sneezing and
coughing within the first few days being at home, and her eyes were clear
and clean. But yesterday I noticed that her left eye is a bit watery and has
puss again.
Then, four days ago (Thursday) I noticed that her poo became less solid,
then on Friday even less solid and on Saturday the same. On Saturday morning
(yesterday) I spoke to the vet, who said it was normal - change of home,
diet, new environment; and that these symptoms are quite common, so there is
nothing to worry about unless it persists.
But, what was particularly worrying me was that she cries when she goes to
the bathroom ... and this is strange cause usually it's the constipation
that is more painful and diarrhoea. But this morning I noticed there was
blood in the litter tray! A more solid poo and blood spot. Is this normal?
Is this due to the change of diet? Is she having her period? (She hasn't
been spayed as yet - due in mid August). Please help, cause I'm worried...