I'd add that I'll bet anyone can benefit from going through their thought patterns applying the insights of congnitive psychology, the therapy side of which says, very roughly, one way to make yourself depressed is to think incorrect bad thoughts about yourself (which includes how you view other people viewing you, etc.).
(Which is not to say there aren't also pure biological causes (see tokenadult's excellent comment: https://news.ycombinator.com/item?id=7530847), family history eventually revealed that's a factor in my particular type of depression, but it's certain that self-applied cognitive therapy from an earlier edition of this book made a big difference for me, it's just not enough.)
If you can't afford to do so privately, and you're in the UK, the advice below should help you navigate the NHS bureaucracy and (eventually) see a therapist.
Start with your doctor, GP will probably attempt to put you on anti-depressants immediately and then leave it at that. If that's not what your looking for, refuse, and ask for a referral to a specialist. If that doesn't work, ask to see a different GP. Eventually you should get referred to an actual psychiatrist. They're also going to want to stick you straight on medication, but you'll at least get an appointment with them now and again to discuss that, but they can refer you to a therapist.
As you may be able to tell from my tone, over the years I've have acquired very little respect for the way the NHS treats mental health. There are a few individuals doing fantastic work, but they've always been hamstrung by the bureaucracy involved in making anything happen.
Don't be afraid of not being depressed enough. I made the mistake of doing that and got to a really bad place before I finally sought help. It's also worth noting that, by the time you actually get in to see a doctor, get prescribed something, and then wait the required time period for the medicine to actually start working, you'll be about 2-3 months out from feeling better.
When seeking depression treatment, another thing that was kind of obvious in hindsight (but not so much at the time) is that no one is going to magically come and save you from depression, not even your loved ones. You have to take the initiative to seek help yourself. For months I stalled because I didn't want to go through the process of finding a doctor, and it really ended up biting me in the ass.
Good luck!
Therapists don't prescribe medication- the best they can do is refer you to a doctor or psychiatrist. They can often answer questions about medication though, and help you decide whether that path is right for you. Therapy isn't about medication, it's a different tool altogether.
I've found that this is one of the big reasons that many people I know don't seek help, or waited (too) long to do so. Especially for people living alone who can acceptably 'curate' their existence when around others, it's very easy to lose perspective on what is 'normal' or 'healthy'.
It's made me wonder if it might be good to consider going to a psychologist something akin to a yearly dentist checkup.
In the US, if you're in college, go to your student health center. They have people who are very experienced with helping students with their issues.
If you're not, check your employers health offerings. Mine has an anonymous number that we can call, separate from HR and management, to get help and referrals. They even paid for the first 5 (6?) sessions before I went to my own insurance.
If your office doesn't have that, or you're not comfortable going through them, go to your regular doctor for a referral.
If you've got friends that you know have dealt with these issues in the past, ask them for a recommendation. You don't have to be specific, you don't even have to tell them you're depressed (or think you may be), just say you need someone to talk to and ask who they went to.