Unlike the modern "western" medicine, which often treats the symptoms and superficial causes, Buddhism is all about finding and removing the root causes of dukkha (~suffering) including its subtype we simply call "stress".
If you think about it, and as the Buddha himself said, all of the Buddhist path is about stopping suffering and arresting causes of suffering. Specifically, the group of teachings known as The Noble Eightfold Path is a collection of methods for preventing creation of the causes of stress at all levels, from coarse to subtle and from social to innermost.
It should go without saying, but I will still say it, that you having lots of stress in your life is indicative of gaps in your practice of The Eightfold Path. Why don't you review it and see what you get.
Leaving that aside, when it comes to meditation, suttas explain that meditation goes in progression from basic to advanced. The goal of basic meditation is to learn to focus, because most people are rather scatterbrained and are easily distracted by their own thoughts. The goal of advanced meditation is to identify and resolve emotional and mental hangups that serve as inner causes of stress.
When I say "hangups" I mean a broad class of issues like prejudices, stereotypes, overgeneralizations, internalized misconceptions, and reifications.
The work of advanced meditation is to
- notice there's something in the fog
- feel through the fog until you can more or less clearly see the issue
- focus on the issue and observe it until its inner workings are clear
- find the abstract core of the issue - the metaphorical handle you're holding on to,
- resolve the issue by letting go of the handle
This process is repeated dozens and hundreds of times, taking whatever next instance of stress that comes to mind and tracing it back to its source in your psyche.
By now it should be clear that basic meditation on single object cannot by itself undo your knots and tangles. You have to work with your actual feelings and their conceptual/preconceptual roots.
Now, what is the role of objectless open-ended meditation and where does it fit in this process. The way I was taught, its role is to serve as the base camp from which the exploration of hangups takes place.
In other words, the objectless meditation, and meditation on breath too, is where you start from, and where you come back to every time you get lost, and after every successful uprooting of a hangup. While having a basecamp is important, if you stay in the camp day after day, your vacation will be over before you climb that mountain and see that bear. LOL, today I'm all over the place with my metaphors :)
I'm sorry to disappoint you if you assumed you can just sit in meditation and it will work by itself. You have to make an actual effort to explore and process your crap. Otherwise you'll just keep churning the same stress over and over.