How to treat my cat's constipation and reduce her fever

I have a 3 years old female cat named Bunny. She was sick last month with same symptom (constipation + fever+licking lip) , and the vet gave her some antibiotic, enema and stool softer. she felt better immediately so I stopped giving her antibiotic after a week which i should finish it.

Last week she had same symptom again so i took her to vet and they gave her same things. Veraflox and Lactulose. they did X ray on her and there were many stools and urine. She went home and pooped immediately so i thought maybe this time she will recover soon. But this time she is weak and not pooped very will. So i went to Vet again and this time they did blood work on her and gave her Convenia injection and some fluids to lower down her temperature. she was 104.2. This happen on 12/26/16. After a day the vet told me her blood work went fine and nothing wrong showed by it. They suggest ultrasound that might cause $500. till now i spent about 700 dollars and I'm a student so i couldn't afford the bill. At 27th morning i saw her trying to go to litter box 3 times and nothing came out. so i bought some wet food for hairball and urine and digestion formula. the Vet suggest me to stop the Lactulose on 26th cause i saw some non-shaped poop on 25th night. Till today i didn't see any poop so I start the Lactulose and some probiotics product today. She do pee but not much. She is weak and has fever, i love her so much but i couldn't afford the bill. Please give me some advices, thank you.

You could try some miralax and see if that helps. Dosage "A common starting dose is 1/8 of a teaspoon per day, though if you don't see an improvement in your cat's constipation after three days, you can increase to 1/4 of a teaspoon if necessary." 

Def keep feeding wet food but I'd avoid any "hairball" stuff. Just feed high protein meat based wet food. A decent cheap one is fancy feast classic chicken or turkey. A good digestive enzyme would be good too. I like this one.

https://www.chewy.com/animal-essentials-plant-enzyme/dp/49372

I'm concerned about the fever though. Constipation really shouldn't cause a fever. 

Lip licking can indicate nausea. Many things can cause nausea so the vet would be the best one to ask more about this and and have more blood work done if necessary.

Vet bills are expensive but there may be ways to more easily afford it. See this for info: http://www.thecatsite.com/a/no-money-for-vet-care-how-to-find-help-and-save-your-cats-life