I'm going to cut off my ex boyfriend who just came out as gay
What is your reason for cutting him off?
I clung to him for helping me with my loneliness
It's understandable that it may be hard for you to accept this major change in your ex's dating preference. However, you shouldn't cut someone off for being gay. You should be there to support him, like they did when you were homeless.
You're right. It's easier to stick with a lie.
You can still be there for someone even if you're not their girlfriend. You don't have to completely remove them from your life or stay their girlfriend, there is a middle ground in this scenario. Try talking to them and explain your feelings and let them know you still want to support them.