Eren is either dead or very near death. Let's do some math: At the time a person inherits titan shifting ability, they have only 13 years to live. It's been 4 years since they reached the Ocean, and he was around 16 then. So he is 20 now (in chapter 91 and 96). Based on analysis, we can say that Eren gained titan ability at the age of 7. So, at the time they reached the ocean, he had around 4 years to live... guess how many years it has been since then.
Tell me what you guys think.