My gf has lower back pains, palpitating heart, and when she holds her breath, allegedly,it stops beating. then, when she gets a bump, it easily bruise?

Ekg & Holter monitor: She needs these tests along with a blood test to monitor her tsh. Also have her stop all sources of caffeine. If she has low back pain, she needs an xray. Easy bruising if problematic, needs further blood tests, including a CBC and a PT/INR

See physician: Low back pain, easy bruising on the limbs and occasional palpitations are all fairly common, and women are often more sensitive to these body events than men are. However, very rapid or prolonged palpitations could be serious, and a breath holding or cough might be able to stop an abnormal rhythm sometimes. Additionally, large bruises on the torso without trauma could also be serious. See doc.