I've been with my partner for 4 years. Not been an easy relationship with petty squabbles but we were engaged at 17 and split up 3 years later. He found me again after 25 years when his marriage broke down. However he is still married and I feel very uncomfortable with their friendship. They don't see each other much but she rents his parents house when they relocated to be closer to other family and they text/speak quite a few times though the week. They have a son, he is 25 and is independent of them both. I can't get my head around why I feel so threatened by her and why I believe in my heart that she wants him back and is just waiting for he and I to fall apart so she can pickup the pieced. She hasn't had a relationship or dated anyone since they split up 5 years ago in October. Can anyone offer any advice deal with this in a rational way please. Thank you hopefully