Hi, welcome to the forum.
I'm sorry to hear that your bunny may be poorly but when you take on the responsibility of any animal you have to ensure that you can affort vet bills. I take it that your bunny is not insured either?
Is there no-one who can help you, like a parent (you come across as young; apologies if you aren't!), other relative or friend even?
If you are in the UK you could try the PDSA or even the RSPCA who treat animals for either a reduced rate, free, or could possibly work out a payment plan for you. Your local vet may agree to some sort of payment plan, although most don't, but it's worth asking.
If your rabbit is really sick and you really cannot afford the bills you may have to consider signing him over to the RSPCA for them to look after, make better, and then rehome.
You have to by law get medical assistance for your rabbit otherwise you are going to make him suffer, which is cruel.
Sorry to be so blunt.