How can i tell if i'm having a mid-life crisis?

"Mid-life crisis": This is not a diagnostic category, but people use this to describe responses to life transitions occurring from age 37 - 50's. "midlife" depends on how old you are & how long you expect to live. Unrest may develop around events like a child leaving for college, death of a family member, a birthday into a new decade, etc. You might consider talking through your own situation with a therapist.

Not yet...: No to sound to sarcastic, but you're too young to be having a mid-life crisis, especially with the increased life expectancy. The question you've asked requires far more details both in terms of what the 'crisis' is making you think about, and what your recent stressors have been, both the small and large ones, and their chronicity... Social support/family/friends are critical...