My dad...I need help. Idk what to do. I need advice.

My mom passed away last January 4th. Since then my dad has gone a little crazy. He's brought a woman to live with him not even 2 weeks after my mom passed. He's been dating a lot of women. (Which doesn't bother me too much anymore.) My mom wanted her ashes spread at her favorite beach. He went WITHOUT me and with another woman that idk for 10 days and released my mom's ashes. Honestly, it's been bothering me. Since mom's gone we haven't had a very good relationship. We don't talk too much. And honestly, I'm scared to give him another chance, bc.I don't want to get hurt. Anyways, I'm 15 weeks pregnant and I haven't told him yet. Bc I don't want him to come back into my life for my child.. I'm having thoughts of telling him, I just don't know if it's a good idea. What would you do??? What should I do?