I've been really thinking hard for the last 6 months about joining the military. I have a degree in health, physical education, and recreation

boy what a waste. I feel like I'm pretty far behind people my age. I want to get into something that will set me up with a retirement plan ect. I have always been a huge fan of the military. When I was little I always played dress up. I still do that I have a closet full of guns, ammo, and other cool shit.
I was thinking of just going for it and joining the army infantry. I feel like I'm the happiest when I have a harder life. When I have structure and I'm making accomplishments. I played sports all through highschool all 3 sports seasons. I played college football. I like working my ass off and then having a couple of hours at night to enjoy just sitting in front of the tv with a fat dip in.
Is 26 years old for me? Last few months I have been running a lot. I'm a pretty damn good athlete once I'm in shape.
Anyone here have any input for me. Thank you.