Period 2 days late took a test came out negative. lower back pain tender breast can i just be paranoid and it's stress delay?(protected sex!)

Yes, possibly stress: While some forms of protection do 'fail', your use of protection and a negative 1st test add up to a good bet that you're not pregnant. It's also a good bet that you are not 'paranoid' - merely sharing a common dread of unwanted pregnancy. Re-test in a few days if you do not begin your period and/or have a professional test/exam. You are correct in realizing it could be stress. Relax - good luck!