How can I get my doctor to take me more seriously? 24M

I have an issue which my doctor agreed I'd identified correctly - I have torn an external oblique and it's making it hard for me to use my right hand for an extended period of time (even carrying light shopping) and it's getting worse. I was told that I will just have to managed it and let it rest. I have been trying to rest it for 3 years with signs now that it's only getting worse.

It is directly visible - it looks like the muscle is missing on one side now and they have not given me instruction on whether there's physio, surgery or anything, just told me to rest it. I explained it doesn't make sense that doing the same thing would make it better after such a long time. They then said it'd just have to be "something I'd manage".

Even explaining that not being able to carry shopping with ones dominant hand would be concerning for a 64 YO let alone a 24 YO and that more recovery didn't make sense, I just cannot get through across 3 appointments now between 2 doctors and I really don't think trying to politely explain this is becoming quite serious is going to work.

When I'm next in this situation what do I do? Do I threaten a complaint? Do I make sure to get their name and ask a second opinion. Is there anyway to make doctors that are not taking you seriously take you seriously or do I just keep hoping for a better doctor?