Hi,
I think you are doing the right thing, but putting your feelings out there and dealing with them.
I find honesty to be hugely important in recovery. It sounds to me like you have been doing really well, and you are aware that your relationship with your child's father, is less than honest. If it was me, and I was sleeping with a man who I wasn't involved with, it would cause me problems. Maybe take a step back from that relationship and from the person you've begun dating, and see how you feel.
Congratulations on 8 sober months!