I have 8 week old twins. For the first time since they were born I went out for the day with my friends. When I got home my BF casually mentioned that a female friend who I haven't met had popped round to help him look after the children. He had prearranged the visit the day before but not said anything. She is married, had no children herself and lives five mins away. They have been on business trips together and he says he has known her for 18 years. This had not been mentioned before. I was very upset but he says I am insecure and slightly mad. I think he has no respect for me whatsoever. What should I do?