I believe both @Bakmoon and @santa100 have touched on it in their answers; @santa100 gives some traditional writings on the subject.
Very briefly, all three of these marks of existence are intertwined in their meaning, understanding, and relation (they're "three sides of the same coin" to completely mess up an idiom!)...
Let's start with impermanence: The idea that nothing just is, that it's instead always changing. Pretty simple fact of physics, mainly. Next, consider Anatta or non-self, which is a way of saying that even what we might call a 'self' isn't permanent, it too is impermanent; meaning, there isn't one (a 'self'), because that would be something! Finally, Dukkha or suffering: That 'suffering' or 'unsatisfactoriness' arises because our mind's habit is to imagine that some things actually are permanent, or that we have selves.
Really, that's it.
So when meditating on the breath, if you 'get' impermanence, then you also automatically get non-self (as you've said) and suffering (because suffering is just the illusion that things are permanent in any way, shape, or form).
Finally, the way I would answer this most simply, is to say that in whatever way to feel you understand impermanence, that would be very closely related to how you understand suffering; suffering is just the 'auto pilot' or 'habit of mind' that arises from not understanding impermanence, at every moment, of every day.
When you're following your breath, you likely have some (slight) expectation that it will continue to go out, or change from out to in, come flowing back in, or finally change from in to out. That expectation has in it the seed of dissatisfaction. At some point, on some breath you take, it will do none of those things; it will stop. Just that slight expectation is an illusion. (Not to mention all the times your mind might wander and 'expect' or want different things from your past or future.)
I (and others, including scholars) feel that 'suffering' is an unfortunate translation and choice of word, particularly in the West, although it is a literal translation of the term used in Pali, Sanskrit, or Tibetan. In the Wikipedia article you link to, the linked article to suffering (Dukkha), includes this gloss, re: neither pessimistic nor optimistic which I find helpful to understand a more nuanced definition of 'suffering' as Buddhists define it. (The above link has changed substantially--so I've edited the link so it now links to the older version as it existed when I wrote this answer. Here is the current page on Dukkha, as it is now.)