Grieving for pet. Help!!

My boyfriends cat had to be put to sleep, he was 16 years old so lived a long life. But my boyfriend wasn’t strong enough to go in with the cat while he was put to sleep, and I didn’t want him to die alone. So I went in and sat with him for his final moments. It was the most awful thing and I’ve cried every night. I didn’t know I loved the cat so much, but now he’s gone, I miss him so much and I don’t know how to get over this.

Its worse for me, my boyfriend isn’t grieving, and he didn’t witness the dying moment, and I’m really struggling to get through this. I don’t want to lean on my boyfriend for support because I don’t want to make him upset.

Please tell me how to get through this loss. I’ve never felt like this, never been this sad in my life and I’m worried it will get worse.