Help, female kitten straining in litter box

Lilac is 5 months old, to be spayed this weekend. Today she started straining in the litter box: sitting with her tail raised for up to 6 minutes, as if waiting for her body to produce something, but all that comes out is a tiny urine (not bloody). She makes no sound, so is not in pain (yet?). I cannot tell whether she's trying to do number 1 or number 2. Help!!

She may be trying to poop, cats will usually have their hind end up a bit from the litter when pooping, and almost sitting on the litter when peeing.

If you think she is trying to pee then she should certainly be seen, asap.

Thank you, Catwoman.

How do I tell which one she is trying to do? If she's trying to poop over and over and nothing comes out, is she constipated? Is that something that goes away on its own?

(I don't know how to Edit my posts here.)

From what you wrote, it seems like she is trying to pee, then. She almost sits on the litter. Oh no

Well like I said, if she is peeing she will almost appear to be suitting in her box on the litter, but pooping she will arch her back a bit and not be so close to the litter in the box. Plus her tail would be up more.

Constipation is caused by many things but commonly it's a change in food/diet.

Lack of drinking enough fresh water, cats are very particular about the water and clean dish they drink it from. 

If nothing has been changed or added with her food, then I would suggest she be fed canned at least once a day, her dry should either be grain free or Natural Balance, which is affordable.

You can, for now add about 2 teaspoons into her food of mineral oil, olive oil or canola oil.

It helps lube things up inside so they come on out easier

She needs to be seen by the vet.

Thank you so much. She was seen by the vet and prescribed antibiotics for UTI. I wonder how she could have gotten it as such a young age...