My hair!!!

I noticed that during my pregnancy my hair would not do what I wanted it to. If I curled it, it would go flat within a couple of mins. When I straightened it, it would feel like I had a bunch of knots. My hair is long almost to my butt. My friend warned me that after I had my baby my body was going to be against me. She told me that she actually lost hair!!! But not me, my hair keeps growing and theres a lot of it, but it's not the same anymore. Why would be the reason to why my hair is acting up?