Then it was "What's the point in doing any work today, nothing matters". Eventually I lost my job.

I don’t think that career was your calling, to be honest. If it was, you’d have little reminders of why it is you want to keep going no matter how mundane it got. Pick the job/career that brings meaning to your life. Don’t think about what other people think or how much money you’ll make. Everything else will fall into place.

I am incredibly bored and unable to make myself interested in anything aside from the odd game or TV series.

I’ve been there. Or, I mean, I am there. Unfortunately, society says we have to keep trudging along. Here’s what works for me:
1) Sleep. A lot. Get at least 8 hours so you'll have a clear head to make good decisions the rest of the day. This is honestly the most important thing to work on, in my opinion. 2) Eat healthy and exercise. It does wonders for your self esteem.
3) Get off the computer. No really. Try to limit screen time to no more than 2 hours a day. They say experiences make people happy, not TV shows or video games, and the only way to get them is by going outside. Speaking of which...
4) Sunlight most days of the week. It'll help regulate your circadian rhythm and boost your mood.
5) Visualize the things that will make you happy. Here’s a hint: it won’t be a gadget, device or other material object. It’ll be an experience. Whenever I get really apathetic and hope I go to sleep and never wake up, I picture the one thing I want to experience that I'll never get the chance if I keep moping around.

I am incredibly bored and unable to make myself interested in anything aside from the odd game or TV series.

I feel this way all the time, but I just tell myself I'm not going to give up until I've at least tried everything I could to give myself a happier future and outlook.