Advice needed please

Hi everyone. My boyfriend and i have been together 9 years and have two children. Three years ago, i found some suspicious looking emails that he and his ex gfriend (who he was still friends with) had sent to each other. When i confronted my bfriend, he broke down and confessed to having kissed her on a night out when i wasn't there. He told me he'd asked her for advice as a 'mate' as he and i were't getting along too well at the time, and the kiss 'just happened'. I admit, i wasn't a very nice person at that time but it was still hurtful that he could have done that before actually talking to me about how 'unloved' he felt. Anyway, after a lot of tears from both of us and anger from me, we agreed to put it behind us and move on. We had another baby last year and started planning our wedding. All was well until i received a strange text from my sister just after the new year. She implied that my bfriend was no good. When i asked her what she meant, she refused to answer, saying it was nothing for me to worry about. Eventually, after i begged her to tell me, she said that she and my bfriend had 'got off' together 3 years ago. My bfriend was shocked and amazed at this, and swore that nothing had ever happened. My sis then informed me she was coming over to 'have it out' with him. She turned up at my house reeking of booze and instead of confronting my bfriend, she became agressive towards me, even challenging me to a fight whilst i was feeding my baby! When my bfriend asked her what he was supposed to have done, she answered smugly: "i have nothing to say". She then started screaming abuse, so my bfriend had to forcibly remove her from the house. An hour later, i got an abusive call from her, again accusing my boyfriend, and reminding me that 'he's done it before'. However she changed her story from them 'getting off together' to him making a pass at her wich she rejected. She told me it had happened 4 years ago, after i found out about my bfriend and his ex. When i reminded her that that was actually 3 years ago, she screamed at me to 'go kill myself' and hung up. I havent heard from her since. The thing is, it has caused enormous strain between myself and my bfriend. I know what my sis is capable of, she once made a pass at our own mum's husband. She has boasted how she can get any man she wants, and critisizes others for not being as 'intelligent' as her. If my bfreind had not done what he did with his ex, there would be no question in my mind about who i believe. Before all this, we were getting along brilliantly, just like when first met. As it stands now, i keep asking him if he's telling the truth. He swears he is. I know he's never liked my sis, he found her vain and conceited. I just dont understand it, not long ago my sis told me how pleased she was that me and my bfriend were ok now. I would really apreciate some advice, as i can't think about anything else. I am so upset and confused, and my little boy keeps asking why i'm crying again.

hi,read your letter and when an ex is still on the scene things will go wrong ,if he ended the relationship she will be bitter and hurt and if she can get her claws into him she will and visa versa i ave my hubbys ex on the scene and it is a nightmare, as for your sister something has gone on there either shes jealous of your relationship and is trying to ruin it,does she have a man in her life?perhaps they both had a moment and he realised what was at risk and knocked her back which would leave her bitter and angry,

hi sorry got cut off b4 i finished, as i was saying the other thing is that something did happen between them and with him denying it has sent her into a rage ,which from experience i know can happen ,she sounds very insecure to me so you either believe your boyfriend and move on or it will come between you,and believe me it will eat you up.