Is it normal that i feel bad when i kill anything

I do feel very bad when killing things in real life, such as bugs and even plants. I just feel guilty about it. I know that plants don't feel pain, but I still feel bad for some reason. When my mom kills weeds, I feel bad. Then I have to kill them, which makes me feel worse. I sometime take little pieces of revivable plants from the dirt pile on the road, where people throw away their plants and organic matter, and propagate them.

And I think I have a perfectly good reason about feeling bad when I kill bugs. I usually try to stay away from killing them, but sometimes, I'll wash some ants down the sink, if they are their. I don't have the time to remove all the ants from the sink... yes sometimes, they trail. Then, I would try to make myself feel better by saying,"Ants, run away from the water, or you'll be flushed." It makes me feel cruel. In a biology project, we had to kill bugs and pin them. The first time killing a beetle, I put it in the kill jar. It made me physically sick, when the insect flew around panicking, bumping into the glass. I almost threw up.
Another time, I remember in elementary school, my friends went out and resolved to kill snails, despite my best efforts to stop them. They sprinkled salt onto the snail, torturing the poor thing. I stayed back when they did that. Then afterwards, I urged them to finished it off, like crush it under their shoe or something, since it wasn't dead yet. I had to do it myself... when they didn't.

But I realized that I also feel bad when I damage inanimate objects. For example, if I kick a hole in a wall after the outburst of emotion, I will feel sorry for the wall. And then I would make a silent apology, like saying "I'm sorry wall, you didn't deserve it."
That causes me to resort to self harm... because I can't release my frustration on other things. I don't feel bad if I'm harming myself....

Okay, so I remember playing games such as Spore or Sims. In Spore, I would always avoid killing the animals and destroying the tribes... It made me feel bad when I killed them. Especially in creature stage where they would run away from you. And you would brutally track them down, killing the babies as well... I would have to remind myself that they are not real.
In Sims, I remember trying out to killing a character, as many people did in that game. I thought it would be fun, but I immediately felt bad, when the sim dies and the grim reaper came. I felt regretful and sick. The sim was crying and begging to not get taken away... why do they make it so emotional?.. As with spore, I had to remind myself that they weren't real.