can you spot and be pregnant? PLEASE READ DESCRIPTION

I've been cramping for 3 weeks and have had pregnancy symptoms. I had major cramping today, like pain running down your legs type cramps. I was sure my period was here. I did spot, but BARELY at all and then it completely stopped. No more spotting or bleeding after that instance today. I'm on birth control but I'm worried that it has failed. My period never happens like this. what could it be? ~I've taken multiple tests but I feel like I'd only be a few weeks along if I am pregnant. All of the tests are SUPER faint positives or negative. I'm getting mixed signals from tests lol~