I love giving my GF oral. I think it is totally normal for me to be so aroused from this. A couple of times I came while doing this; I guess I was humping bed at same time. She really didn't like this and suggests that there is something wrong with me. I really doubt that. How many guys have cum while going down? Thx!
I'm not a guy, but I can give you my opinion on the situation. I think it is normal for people to get aroused from giving oral sex. There is nothing wrong with it and nothing wrong with you. If people can get off watching it, I think you can also get off giving it to someone.
Why does your girlfriend not like it when you cum while giving oral? Maybe it would be wise to talk to her about it.
In my opinion, it is a little give, a little take. You give her oral, giving her pleasure, while you get off to it, giving you pleasure. Everyone has their own groove, you two just need to find a happy medium to meet both of your needs.
Hope this helps!!