Started throwing up and having diarrhea with chills last night. also lower back hurts so bad body keeps randomly having spasms and legs feel weak???

Start hydrating: It sounds like you have a viral gastroenteritis . You may be feeling weak from dehydration of electrolyte deficiency (low potassium after vomiting). I would suggest drinking a sport drink starting with frequent sips. Keep your diet minimal - limited to bland, non-citrus foods, non-oily foods and advancing as tolerated. You should be able to get potassium in diet.