Time management

I have trouble managing my time in classical. I always end up blitzing out my moves, for instance, when I play 1.e4 I am very quick to make my next move, and as the game goes on I still take very little time to make my moves. I do think about my move but it is still pretty fast, maybe a couple of seconds to a minute. When I play 10+0 I find myself running low on time, but when I have all the time in the world I am playing a blitz game. What can I do to make myself use the most out of my time instead of being rash and making quick moves? I already do think about my position but maybe I just dont understand it enough if I am still finishing games with 20+ minutes on my clock

I have this issue, and it's annoying.
What I have found helpful is changing your setting to require move confirmation. I actually did this on the advice of someone to stop with mouse slips and a misbehaving chess site. But it does slow you down. I've also a sticky note on my page reminding me to slow down and ask myself 3 questions.

1. Why did they do that?
2. What should I do about it?
3. What would their response be?

Doesn't always work, tho.

How would you play if you played a game for your life?
Chess is a very complicated game. Top grandmasters who know more about the game think long before every move, also in the opening. You should think lo,ng even when you know the moves, so as to reach a state of concentration. How can you play fast? Why? Do you play impulsively? Control the impulse. As they advice youngsters: sit on your hands. Lasker said: "If you see a good move, wait, do not play it, you might find a better one" Enabling move confirmation is good.