I am so sorry to hear of your loss. It must be so very hard after so many years together. I am sure you must feel terribly lost.
As Emz says, suffering a loss does change you, but it sounds like it is still very early days for you. I think losing someone close does make you feel very vulnerable and it certainly leaves you in shock. In my experience, it takes a long time to get past those feelings to any real extent. They say the first year is the hardest. Perhaps it is, but I find there are waves of days when it all seems worse than other days.
Be patient and gentle with yourself. Certainly for at least the first six months, I wouldn't expect to feel much better. Just concentrate on surviving. Remember to eat and drink, but other than that, just do whatever you need to do. In time, acceptance comes and slowly you find a way forward. Just take it a day at a time.
I expect you probably are stronger than you think, but you have just suffered the worst blow that you are ever likely to, so it may take a while before you recover any of that strength yet. In the meantime, we are all here for you to help support you.
Sending hugs...