Cars51, I commend you for being open and reaching out! There's a been a lot of really good advice offered here, and I want to thank all of you, the BITOG community at large, for your comments. Once again, you've proven to be a compassionate and wise bunch. (But Cars51, no, I wouldn't get rid of the Camry! I'm sure that was said in jest. What IS depressing is a car that breaks down regularly.)
Besides anything else that any of us have said or will say here, I want to reinforce what several others have already said, that you should see at least your family doctor for a start, and consider professional counseling, etc., from there.
So having said that, here's my eight farthings (two cents):
Others have mentioned Vitamin D - it is essential, and we get very little naturally (from sunlight) here in the winter. So, October into at least April, I pop at least one pill (1000 IU) daily, and sometimes more.
Vitamin B - I didn't know about this, but it looks I should be taking supplements - I am near-vegetarian, and seldom eat any red meat, which looks to be the best source. I do take a multivitamin for old geezers; I just checked and it does contain a range of B vitamins.
Omega 3 fatty acids - I grind flax seeds every morning and eat them with my mush (oatmeal). Someone please correct me if I'm wrong, but I believe the flax oil contains ALA, which the body metabolizes to form DHA and EPA. Fatty cold-water fish (salmon, mackerel, etc.) already contain DHA and EPA. I prefer to go the flax route. The ground flax goes rancid very quickly, so I prefer to grind the flax right before eating it.
Our short winter days can definitely be a downer - around the winter solstice, the sun is not rising until almost 8:30, and sets before 4:30. It's dark when I get to work, and dark when I leave. BUT, I almost always got out for a walk with some of my buddies. We do about 3.4 km (a bit over 2 miles). (I keep forgetting; this is a bit past-tense, as I retired at the end of January.) This is not about getting Vitamin D from the sun - it's about getting enough light to stimulate the pineal gland. (Apparently the skull is relatively translucent, and lots of light penetrates besides through the eyes.) We have a SAD light as well - the brightness of the light, not its source, is what is important.
Exercise is absolutely vital - unfortunately, when you're feeling rotten, exercise is about the last thing you want to do. Make yourself start something. I'm glad you're out playing hockey - I'm jealous; I played for a number of years, and still miss it. I used to run a lot as well, did a number of marathons, but that takes a toll. I now enjoy skating on the river trail, ride a fat bike in the winter, and a mountain bike or a hybrid three season.
I'm glad you're in a relationship - we are, by nature, social creatures, and it's good to have someone to share our lives with. Besides your wife or girlfriend, it's good to have other friends. I'm very fortunate that way - I was quite close to a number of my coworkers, and have good friends from church and past jobs. But, friendships do take time - I am aware that I need to invest in them to keep them healthy.
I'm fortunate in that my wife and I have a very good relationship and are able to laugh together quite a lot. Speaking of which, it's great to be able to laugh about something until you cry. I don't know if laughter is the best medicine, but it sure helps! (My friend sent me a very abusive thing about our Prime Minister today, and I laughed myself silly.)
Different friends fill different roles - I've got my buddies to discuss ancient sporting events with, to wrench with, to cycle and run with, to talk theology and rant about politics with, and to swap books with.
Animal friends can be very good - we lost our beautiful rescue dogs a few years ago, but now have a pair of fine farm cats. (I've gone from dogs who adored me to cats who tolerate me.)
I don't want to violate the R part of RSP, but have found that being part of a faith community to be excellent for my well-being. Part of that is learning to be thankful for one's blessings. I'm getting better at that.
Meaningful work is important - I was proud of my company (a hydro-electric utility) and the work I did there. It's about more than the money - if your work is not satisfying, look around for something that is.
Hobbies are great - I love wrenching on our vehicles (no surprise on this forum) including our bikes, love to build things (new stairs for the deck, planters, etc.), enjoy house wiring, like studying math and electronics nerd stuff, reading fiction, and so on. What do you like to do? If you're not really sure where your interests lie, consider taking aptitude testing - this was a long time ago, but in university I took something called the MMPI in which my responses were compared to those of people in different professions who purported to be very happy in their professions, and the counselor was then able help me sort out who I really was.
I went through a devastating loss a few years ago, and doubted that I'd survive it; I think only my obligation to loved ones kept me hanging on. I say that not for pity but to say that some while later I was installing a hitch on a unibody car, which involved an intricate procedure of installing bolts blind through channels. When I got it, this satisfaction surged through me, and I realized it was the first time in quite awhile I'd felt anything except unbearable pain. Wrenching (or probably anythng else constructive and tangible) can do that for you.
This was over five years ago, and life has gotten much better. It will never be the same, but we've done some wonderful bike trips, I've blundered through a number of tricky car repairs, we've gained a lovely daughter-in-law, and recently a beautiful granddaughter, and I was able to finish my career with pride.
I guess I'm saying that things do get better. Please PM me if you want to correspond directly.
Sorry for such a long blathery post - I hope some of it was helpful. Please keep us informed as to how you're doing! My sincere best wishes to you, Cars51! (P.S. Keep yer stick on the ice!)