You don't need to have full blown PTSD to be able to get help. And yes, a lot of women do go through the same thing and don't get effected by it long term, which is why I didn't know it was a "thing", I thought you just got over it. But it depends on what happened, how you felt about it, even afterwards it can kick in, and how you perceived it or how it was handled. It doesn't make it any easier. I think compassion, explanations and communication are crucial to the woman and how she then takes that and deals with it afterwards. If you don't have them from the staff it can play a part in how it's processed in your head. They're bigger factors and more important than midwives / doctors think.
Yes, I did say half way through having help "maybe I should think about having that other baby I wanted" but then realised I only wanted another so I could "get it right". That's not reason enough to have another. There are ways of healing without going through another birth.
I thought the same as you, if I knew then what I know now it would have been different. But... the way the birth went isn't your fault, you didn't know what was going to happen. From the point of conception, that birth was waiting for you all along. That's what I tell myself. Sometimes there are things you can't control. I couldn't deal with another trauma. It would break me. Especially if the worst actually happened just because I wanted to have the birth I wanted with my son. It's normal to think about 'what ifs', I did, because I blamed myself. But as I went through the whole thing bit by bit and actually acknowledged it all, it was down to the midwives and doctor.
I thought I was over reacting too... I suppressed it because I just didn't know what to do with it. There wasn't a "controlled" environment for me to let it out. So I blocked it out. Didn't talk about it. My stomach turns if anything about the NHS is mentioned. I'd panic if OBEM came on by accident and I was just angry about everything to do with birth, hospitals midwives etc. I couldn't do anything about it, but when my sis had her baby she had the midwives round, then I started panicking. Went home, thought that's not right surely women don't live with this. That's when I Googled getting over birth. A load of stuff with trauma and PTSD came up. I read the symptoms and cried. Went from there really.
I'm just trying to say don't think you're wrong about feeling the way you do. It's natural and normal if you feel effected by it. If you find yourself questioning it more... then I'd suggest gong to the GP and asking for a referral. Because it can fester. 
I am rambling a bit but I don't think you can ramble too much about birth trauma. It's good to actually talk about it and your emotions because it's such an important issue and I don't think any mum should be left on her own to deal with it. It doesn't help when medical staff aren't even aware of it themselves when they are the ones you go to for help.