Firstly, work with your health care providers. ADHD medication works well, even though it doesn't really feel like it works. (Even now I feel like my medication doesn't really do anything but if you compare my life before and after it's night and day).
Reading your post, it looks like you're having a rough time. Job hunting isn't easy, especially when you have ADHD. Rejection hurts for even the most well adjusted people. When you're feeling low it's very easy for your thoughts to spiral out of control. Try to notice when and how this is happening. For example:
Me: "I'm 36, I'm too old to ever get hired!" Also me: "Is it true that no one over the age of 36 gets hired for jobs? Do I know anyone in my life who got a job over this age? Oh, my uncle was laid off 5 years ago and he got one."
There are many different cognitive distortions like this. You can google to find examples of them or work with a therapist to help notice them. Try reading "Feeling Good" by David Burns, he has lots of good examples to draw from.
It might seem a bit counterintuitive, but being kind and forgiving of your shortcomings can often make you more effective and productive. Imagine procrastinating for 4 hours in the morning and getting nothing done. It's easy to think "Damn, I'm worthless. I just can't focus. I can't stay on task. I'll never get a job at this rate." Now you feel awful. When you get back from lunch, you're much more likely to procrastinate to distract yourself from these negative thoughts and feelings.
Instead, try accepting and forgiving yourself: "I didn't do anything this morning. It happens sometimes. I'll try to just doing a little this afternoon and see how it goes.". It's true, you might still procrastinate, but you have a better chance of getting to it now that the negative emotions are smaller and more manageable.
I also recommend Taking Charge of Adult ADHD by Russell A. Barkley as a good handbook, especially if you've been diagnosed recently.