Trying to focus on the medical niche as I have previous experience as a nurse. Have tried cold calling, paid ppc advertising, cold emails, warm emails, reaching out to networks, fixing my website, optimising copy, tried getting part time employment at an agency, improving my portfolio, having no portfolio, reducing prices, raising prices.

Here's a couple things I would consider before quitting:

01) Are you going after the right clients?

You may think you're going after the right clients, but if nothing is working, you may want to consider the possibility that few people need/want your service. It's possible that some medical businesses might not feel the need for a strong web pressence if 95% of their referals come from word-of-mouth or a pre-established referal network. There may be money in some areas of the market, but not others. Look at other developers working in the medical area and research what specific types of clients they're going after.

02) Are you maximizing your income potential?

Look at your pricing and service offerings. Are they in line with the market as well as your financial needs? There's nothing wrong with being an outlier – as long as you can justify why. Are you doing one-off jobs or are you trying to negotiate retainer packages and on-going work? Reoccuring monthly income is always preferable, so if you can put together a retainer package you should do that. You also need to make sure you're charging what you need to charge to meet your financial goals. The per hour rate for a freelancer is going to be much higher than that of an employee. There are plenty of good articles online about pricing. There's a guy named Brennan Dunn who has a book called "Double Your Freelance Rate". It's a good read, and maybe something you should look into.

Anyhow… those are my two suggestions. Hope they're helpful in some way.