Period & Birth Control Questions?

So I've hard sharp pain in my back lately. I haven't had my period since September 2nd 2016. Got off birth control like 5 months ago or so was on the implant. . Have been having unprotected sex since then. But I don't want to take a test because scared it would be negative I'll be heart broken. Could it be normal that I missed my period since ive been off birth control for only 5 months