Can my Plott Hound be pregnant and still in heat?

My Plott Hound is named Lady.I found her in the paper.She is full blooded.Brindle in color.She is in heat and a er spaniel is trying to get her pregnant.He can't reach her though I hope.Her belly is hard and she does not want no one toughing it.Is she preg?Can the er get to her?She was in heat before I knew she was and got out of my house one day and was gone about an hour or so.So is it likely she is pregnant?Could she have gotten preg.from another dog she is still trying to let the er mount her.Can she be preg. from another and still want to be mounted?If anyone has the answers please let me know. Thanks,Sylvia