Confused and hurt!!

So my boyfriend and father of my unborn daughter just confessed to me that he so called business partner and him have had a sexual relationship and that they haven't used protection since she showed him her std paperwork!! He tells me it's only happened 3 times but I'm still hurt and feel disgusted and he's the primary source of income because I am on medical leave due to high risk pregnancy I do love him but I love my children and me more! Never knew it would be this hard telling someone they need to pack up and go :'(