Breakup Advice

I’ve been dating my girlfriend for about over 4 months now and I’ve realized it’s becoming a toxic relationship. We both have mental health problems and ptsd which makes it difficult to support each other. Every time I get close to breaking up with her, I’m afraid I’m making a mistake. I think we both deserve to be happy even though I love her more than the world. How do I talk about breaking up? In my heart it’s the right choice for me. Thank you💕