I would suggest taking a second test to be sure, but the line showing up means that the target of interest (ex. pregnancy protein) is present.
Faded or "light" lines can be due to a variety of issues, but basically boils down to lower concentration of target reaching the colorimetric reagent.
I've always kept a bowl of watsr and dry food filled and then given them wet food once a day.
Never had any issues with them throwing up. Hopefully, someone else can provide insight into that.