CG, I don't know what to say, it sounds like you had a terribly rough go of it and had to endure a nightmare of a childhood being belted a lot and getting your hair pulled by hypocritic parents.
Did they ever give you an explanation for their behavior?
No, they did not ever explain it. My mom said we should not talk about the past (yet she apologized later for hurting me), and my dad said he did not remember a lot of stuff that he did (yet he apologized as well).
How long did they treat you that way?
My mom treated me that way until I was about 15, which was the age I was the last time I cussed her out. I figured out after getting smacked around enough that I did not want to be around. At about that age, I started sleeping over at friends' houses way more often to be away from home, so my mom was somewhat nicer toward me because I barely spent time with her. My dad stopped belting me when I was 10, but he still would cuss at me until I was about 16. When I was 16, I worked at a fast food place after school, started buying some of my own groceries, and was sleeping over at other girls' houses almost every night. My parents started to see me differently, because I didn't need them as much anymore, so they both decided to treat me even better after that.
Did you know what would trigger them to lash out in the manner they did or was their behavior random and unpredictable?
I was a pretty good kid who was sweet, sensitive and quiet. I loved to read. I remember when I was 10 (shortly after my parents divorced), I started going to the public library every single day with my friends after school for hours because I felt like my mom did not want me around. Normal kid stuff would make my mom lash out. There were four of us kids, and if we were too loud or we ran instead of walking we might get slapped. My mom was shameless, and she would smack us around in public and scream at us. Strangers would scold her for it. She let her anxiety and depression get the best of her, because until I was about 16, she refused to admit there was anything wrong. I have the same conditions, but I went to therapy so I would not act the same way.
My dad lashed out because he was a control freak. He would hit my mom as well until they divorced. I remember one time he belted me really hard upside the head when I was about 9 because I looked up at him from a book that he had told me to read. He hit me much less than my mom hit me, but the belt hurt a lot worse and left more redness. Then there was the cursing, "You fucking idiot," or "Don't fucking do that," or "You know, your mom is a fucking bitch," etc. Or one time, when I was also 9, I did not bring a houseguest some water when he asked me to (because I thought someone else was getting it) and he told me that next time the guest came, he would rip off my dress in front of him to humiliate me. And that was not the worst of it either.
And they called themselves Christians. The weird thing is, my other three siblings are still Christians. I am the odd one out.
Anyway, that was part of my joyful childhood, filled with ponies and rainbows.

Now you know why I take the parenting classes, read the books, and take studies on corporal punishment very seriously. Many children are smacked with a hand or hit with a belt, and they grow up to have problems too. I don't spank my son, and he may act up occasionally, but he is a good boy. I think corporal punishment should be eliminated by parents as a discipline method because as long as it is thought of as OK, some parents are going to be more forceful than others. Some (like the judge who beat his daughter) think that they are being good parents, and they don't know when to draw the line with hitting. That is why I say no spankings for my son. It is better to have a clear line drawn rather than leaving room for a mistake.