25 is very low. You should be over 70 at least but 90-100 would be awesome.
Go out and buy some liquid vitamin D. The more concentrated it is, the better. Start taking 10,000 IU per day with food. Your doctor will probably instruct you to take a ridiculously small amount, like 1,000 - 2,000 IU. That won't be enough to replenish your levels, especially at this time of year.
If you do 10,000 IU daily, after a week or so you should start feeling better -- that's if vitamin D is the reason.
They should really rename vitamin D. It's actually a hormone, not a vitamin. We can't thrive without it.
Yes, my personal experience is that, back when I was D deficient, when I discovered I should be taking it, my mood improved right away. I also had more energy and my teeth got healthier. My only regret is that I didn't know I should be taking a lot more until later on.