How can I help a sick stray cat, and where can I find affordable treatment for her?

Back in December, during the rain, I let a pregnant stray cat stay under the parking lot with a little cardboard setup. Sadly, all her kittens passed away. She was really young herself and probably didn’t know how to care for them. Since giving birth, her stomach has stayed big and keeps growing. I tried giving her a dewormer mixed in food, but it didn’t help. She is lethargic, doesn’t meow much, barely moves, and her big stomach seems to weigh her down. She doesn’t play or chase around moving stuff. I’m currently unemployed and don’t have much money, though my parents can help a little. I want to take her to a hospital, but I don’t have a cat carrier, and most are too expensive. She also won’t sit in a box, and she’s too heavy to carry in my lap. Any advice on affordable home visit services, affordable hospital, NGOs, budget-friendly carriers, or how to transport her?. I have never frosted pets and don't know anything about vetinary clinic or hospital..My dad is already pissed at me for sheltering her. I can't let her go like this she won't survive outside.