POCD vs. Pedophilia

I'm not sure if I just suffer from the worst form of OCD or if I'm really what scares me I may be.
I'm a female teenager. I had OCD even when I was ten or something, but it was very different, and I didn't care about it a lot. Then it stopped for a couple years, but last year it came back in a worse form. Firstly I was thinking about someone else they were a pedophile, and I hated it, but I never imagined these thoughts could connect to myself. It started when I was going home from school. I was sitting in a bus, and I suddenly remembered some of my childhood experiences. Mostly that when I was a kid, I liked to help younger kids or just be friends with them because I found them sympathetic. They were usually a year or two younger than me. I got so scared, but after doing some research, I realized that it's nothing bad actually, so I calmed down. But then it came back. I have a younger sister. She's twelve and puberty hit her hard. She already has big breasts, butt and wide hips. And I sometimes feel I wanna touch her, and when I imagine it, I feel like I might like it. I feel unwanted groinal arouse, but my mind instantly reacts that it's very bad, inappropriate and so on. I realize it's horrible and I hate it. I'd never do anything sexual with kids, because I don't actually like them. I've always been attracted to grown men or boys my age. My bedroom wall is covered by rockstars who are all adult men and in movies, my favourite characters are never kids. Everytime I hear about kids, I feel uncomfortable. I think I'm a horrible person when I think a little baby is cute. When I think about having a possible sex with a kid, it doesn't arouse me at all. I hate myself for everything about this topic that comes to my mind. I don't think about kids unless I hear about them. I know intrusive thoughts like this are sign of POCD, but what I feel when I'm around my sister, makes me think different. I love her, I wanna hug her and stroke her head, because she's my sister, but I feel also very uncomfortable around her. I think I once touched her on inappropriate place on purpose, and I instantly thought it was bad. When I was younger, I was doing it kinda often, but not because I found it sexually attractive. Now I'd never do that. When I look at her body, it makes me uncomfortable. I feel like I have to look, so I do it, but I don't like it. I like looking at her face, because I think she's beautiful, but I don't wanna have anything sexual with her, my cousins or other little kids. Only with boys my age.
I'm planning on seeing a professional, but is it even worth it to ask them about this? Could it all be real POCD or am I just a monster?