I am 2 weeks late for my period. I am under a lot of stress and also suffer from dysthmic disorder. Is my late period stress related or am I pregnant.?

Could be either. Get a pregnancy test to be sure. You can go to your doc or get one over the counter. If you are not pregnant, stress can definitely affect your cycle.
Late menses. You are describing what we call "secondary amenorrhea is defined as the absence of menses for 3 consecutive months in women who have passed menarche. The causes of secondary amenorrhea include pregnancy, pituitary causes, glands above kidney, uterine causes, premature ovarian failure, and menopause. All require evaluation. Pregnancy is the most common cause for secondary amenorrhea. So get a test.
Significant stress. Can delay menses. Pregnancy is another possible cause. You can take a home pregnancy test now to know one way or the other.