Drinking dirty water

[sl07]

I've just been to the local pub with my partner and I tasted something "off" with my cola - it was like the cola had been left there a long time and it just tasted like dirty water.

Now I'm worried, I'm in my second trimester of pregnancy and now I'm thinking I've just drank dirty water :(

Did it taste flat? It's possibly that the gas had gone. Or if it tasted weak, that the syrup needed changing I have spent too long working in pubs
Neither are dangerous but both taste a bit weird/off