I'm sorry to hear about the situation you're in. It sounds like a very frustrating and difficult situation. Here are a few steps you can take:
Contact a professional building inspector or surveyor to come and assess the work that has been done. This will provide you with an independent report on the quality of the work and whether it meets building regulations.
Contact a solicitor or legal advisor who specialises in construction law. They will be able to advise you on your legal rights and options, including whether you have grounds to sue the builder for breach of contract or negligence.
Contact your local authority's building control department to report the poor quality of work and ask for advice on what to do next. They may be able to provide guidance on your legal rights, as well as help you to resolve the issue with the builder.
Document everything - take photographs of the poor quality work and any damage that has been caused to your property. Keep copies of all correspondence with the builder and any professional advisors you consult.
Finally, try to remain calm and objective throughout the process. It can be easy to become emotional and frustrated, but this may not help you to resolve the issue. Instead, focus on finding a solution and taking steps to protect your property and your legal rights.