What Causes Dizziness While Standing,chest Tightness And Darkening Of Veins?

Hi there I have these symptoms and need help cause I m scared ; when I stand up not sat dow I feel really light headed and feel like I m going to faint, the veins in my hands are turning black When I stand up and my heart/ chest is tight and shooting pain in them and my hands tingle and lose control and now my feet and legss are losing contol when I stand up ive recently had a miscarriage 3 weeks ago and was bleeding black blood please can you tell me what to do or what this is please