Starting Fresh

Ok so I'm planning on leaving my relationship because there is no way it will get better and I'm trying to create a healthy home and environment for my son. I cant do that while being with his father. I have found shemale dating sites in his email account and other dating sites. This has been a constant thing and I'm just over it. My son deserves a better father and better home and role model. Its some things he does that lets me know he is gay. I mean you know the person you are with and what seems off. Right? I seen messages between him and trannies and i figured thats what he likes and I have not been with him sexually because im scared for my life. If he wants to live that kinda life kuddos to him but my son will not be apart of it im sorry. I have to leave the relationship has been dead for a long time. Just wanna know how you all seemed to start over or the steps you took after leaving your partner and decided to raise a child by yourself. He wouldnt want joint custody he has 3 kids by 3 different women and isnt a great father. And tried to make us hate one another despite our kids being siblings. Just wanna start over as a single parent but dont know how