I'm sad, about something that happened last year?

Ok well last year, a week before Christmas, my dog……… drownded(? U get the point) well she was like my sister and I felt really close to her even though she was a dog. I'm emotionally scar-ed (wait let me tell u the story. Well she was loosing her eye sight so she um kinda fell into my pool, the first time, thank god I was out there with her, she swam to the steps but the second tome is when she passed.) and everytime I think about it I get really sad bcuz (I think I have a problem with seeing and feeling things that could happen) I feel her pain, and I see it. It was so heart breaking to see my mom in tears before we burried her. And my poor dad feels like it's his fault. I think I'm gonna cry right now. I feel so sad. Is this normal? I've lost other family members, even my grandparents, and I get sad when I think about them, but I cry everytime I think about my dog. I'm really sad and my friend made fun of me about- so i told her off- and that made things worse, it's like a nightmare that won't end. Why do things have to die!!!! It's so sad!!!