Killing animals definitely is anti-social behavior, but doesn't inherently mean you have ASPD. If you're wondering if you have ASPD or not you should definitely take this up with a therapist. There's also always a possibility of having an attachment disorder, such as reactive attachment disorder (RAD). It's actually common to find children with attachment disorders having had tortured, mutilated, or killed animals. Children are naturally reactive, when they're being hurt, they adopt maladaptive coping skills and mechanisms to survive the environment. They also act out by imitating same harmful behaviors they're subjected or have witnessed others going through.

Stay safe, OP. Remember that you're not a bad person, you're someone who has just done things you're not proud of. The point is we grow from our mistakes and move on as stronger people.