Antibiotics are known to be big culprite for gi upset and the problem you are describing can be because of the antibiotics which you are taking for UTI.
But the problem which you describe for vaginal discharge
is something which I think is not associated with the use of anibiotics. If you are suffering from UTI than it is possible that the vaginal flora
is also compromised and may be causing this type of discharge.
Thanks and hope this help you.