I feel like i did completely nothing in my enlistment as a Marine.

26m i served 4 years as an 0111 admin, coming outta hs i just wanted to do something and for some reason chose whatever mos i could get. I feel like in my time in i did absolutely nothing but go to clubs and do the most minimal tasks in my actual mos. To make it worse i never got security clearance to be able to use MCTFS which is like what a rifle is to an infantryman but in the admin realm. I really want to get back in the military now with 2 kids (a 3rd one coming) because right now civilian life is taking a shit on me and im tired of working low wage security jobs. Does anyone feel the same about their time in?How can i make the most of it if i do decide to go back in?