5-6 weeks pregnant and Had brown spotting an now blood with lower cramps

Sorry you are going through this, bleeding does not always mean pregnancy loss but its always very scary to see. Brown blood is old blood and quite common but if the bleeding is now getting heavier, contact your doctor. While there is no way of preventing a loss if its going to happen, they may at least be able to check your hcg levels via blood tests and make sure that they are rising correctly. Thinking of you, wishing you all the best.