I never had this with my DD - the other day I drank some apple juice and about a minute later I had this awful taste in my mouth. I thought the juice was off but it was fine. I've had this now for about 3 days and it's pretty much anything I eat or drink. It's horrible!! (I'm 20 weeks as well so it's definitely not that early pregnancy metallic taste.
Hope it's going to go away coz eating is my only pleasure now!