Need some advice please

So on Thursday night I had start of my period where was just spotting woke up Friday morning and was abit more then just got abit more on during day then Saturday was normal then Sunday was slowing down by Sunday night it was gone and it full on gone today.. all today I've had lower back pain and was going all way down to my bum last time was like that was when I was pregnant I did a test today as period was a lot shorter than normal oh also was period was almost 3 weeks late aswell I did test when I was late and was negative I was just wondering if anyone had something like this and ended up being pregnant or just needed up being a normal period?