Confused about my brain?

Normally like to be a "nice person" doing things to help others in need comforting people in distress just over being nice but for some reason I also feel sadistic I strongly enjoy others suffering to the point its basically a turn on. I really love causing minor inconveniences for people like not changing the toilet paper roll, leaving just a little sliver of milk left so someone else has to change the bag. It also goes way deeper, of course naturally I will never engage in these acts personally cause I really dont see it in my best interest to go to prison but I really really like watching gore videos, beheadings, being crushed by large machines etc but here's where I get really confused in real life situations I do what I can't to save a person cause I dont want to see them get hurt or even worse killed, I don't boast about what I do good but say for example I pull someone out the way of getting hit by a car. Does anyone understand why my brain is like this?
Confused about my brain?
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