Wow, I will try to be constructive but I will also be perfectly blunt. I think you need serious therapy as soon as possible. Your son can surely sense that he makes you want to "throw up" and your gender expectations are damaging to him (and any other children you might have). As a "girl" I take offense at the title of your post and your assumption that men and women are supposed to have different activity levels. I a strong, athletic woman. We all have strengths and weaknesses and should be valued for who we are not what others expect us to be.
Beyond your very out dated and wrong headed gender issues, I don't know what is going on with your son - he could just be less active or there could be something happening. But either way you putting pressure on him will not help. There are two things possibly happening right now and they are both awful for your poor child.
1) It is possible that he just isn't that active in which case you are sending him the clear message that you don't love him for the person he is. What a truly terrible thing to express to your child.
Or 2) There is something going on with him (maybe gross motor delay or some kind of sensory processing issue, or maybe something else entirely) and rather than helping him work through his issues you are showing him that you can't be counted on to support him.
I hope the responses here will encourage you to reevaluate your own issues if at least for the sake of your son.