One thing to consider deeply in those moments is that, looking inside and finding motivation, answers, assurance and all is never the easy process some books or gurus insist it is. Looking inside demands time and effort, and sometimes you'll still find difficulty in investigate that vague
"what's happening here" question by yourself.
I've always had small existential crisis from time to time, every since i've started working. But 2 years ago i found myself in a situation of extremes. A true existential crisis that had elements from every part of my life involved, work, family, studies, you name it. It's not that it was all bad things happening. Some of them were good things, but they were conflicting with each other and turning decision-making and focus really really hard to achieve.
For my part, i've made part of my life to visit a psychotherapist once a week. Despite the bad fame of being vague, overpriced and not really useful, i found psychoanalysis to be a real help not only when crisis hits, but also to as means to foresee them and prepare to deal with them. And also investigate myself further when i'm not in a crisis.
There's two very nice things about psychoanalysis, ihmo:
One is that you are the only one responsible for your "treatment" and a good therapist will never try to help you in anything other than investigating your self, your aspirations, your past, your relations with people and with things.
The other is that the therapist is a person you'll only see in that time and space. They won't be your friend (so they won't "care" for you as a friend would), and they won't pretend they are family to you (so you won't have to please them in anyway), and that is precisley what gives you liberty to talk about anything, or nothing, without the fear of being judged. Heck, isn't that why we're sharing things with strangers on the web instead of with friends and family?
The therapist's job is to orient you, asking the necessary questions and pointing the intricacies, vaguenesses, and controversies of our thoughts, but never handing us the anwsers (which they also don't know), so that the process of finding them, when they exist, is also constructive - and so that not finding them doesn't block you from living your life the best way you can.
That is much like a professor would orient your thesis pointing loopholes on your subject. Except that the subject is you, and a little methodology to investigate yourself always helps.
Best of luck!