Having let down feeling recently & slightly crampy on & off.. tester but was negative. Could it be early pregnancy?

Sometimes during the second pregnancy you do get early symptoms of being pregnant quicker. With all that you're describing, it sounds like it is possible that you might be pregnant. Since you're considered 4 weeks pregnant when your period is due), I'd give it another four or five days and then take a test if your period doesn't make its appearance.