Positive Rubella Test :(

Today we were notified by my gynecologist that my blood test for rubella came back positive...I'm now 13 weeks but I would've been under 12 weeks at the time of exposure...I don't know when I was exposed to someone with the virus? The doctor said the tests aren't always right and they're doing a second one today but I'm still freaking out to the max!! We also aren't sure if I had my rubella vac when I was born so we're just holding thumbs at the moment...should I be worried??