What do i do if i dont love my wife anymore?

I'm 26 and got married b/c my wife was pregnant at age 20. She kinda forced us into marriage. (which was thru a county store). Now i thought i loved my wife so i stuck with it. now 26 with 3 kids, and obviously never learned from my first mistake. Now things are difficult and we've been thru all the trials and tribualations of marriage, from her accusing me cheating to everything else. but ive been faithfull, mostly bc theres no temptation. I try everything to rekindle nething. but its no use, shes always tired, headahce or w/e excuse she can think of. its mostly about the kids nemore and were hurting finnacially. I look at pictures on the internet of girls (clothed) just having a good time, parties. and im constantly thinking about a life i never had. My wife dont get this,. Ive talked to her numerous times. She never lets me go out with a friend b/c i would be leaving her home with the kids. when i before have watched the kids while shes gone out and had a good time....so the questions is...how do i tell her i dont love her anymore and how can i show signs to give her?