Feeling totally alone and lost

I am by last period date 14 weeks +1 but after a bleed abd internal scan im measuring 11 week's + 1. so after breast cancer February 2014 I'm 15 month's in remission I've got fibromyalgia and suffer with a mood disorder and depression, that's not so much the issue, good friday I got a message from this girl saying she's in a long term relationship with my partner my miracle baby's daddy. So shocked and sickened I started asking questions only to be made to feel like I was to blame and being told that although he was originally very happy and said baby was and blessing and and gift from God after my I'll health being so bad it's all to soon and no straightforward answers from him about this secret life. This has had a terrible effect on my metal health and state of mind not to mention my future happiness. So scared of losing my mind like before because I'm not medicated at all because I'm pregnant. Feel like I want to just switch off and hide away when I should be happy. I have 2 older daughters who loved and worshipped my partner and the youngest asked him to her step daddy I cry just thinking about it all.