How can I let him know I won't leave again?

I’ve been with my boyfriend for 8 years. I am only 21. We have three kids together. About 3 weeks ago i packed my bags and moved to my mom’s house i was just so mad because i just had a baby i felt like i was doing it all on my own.. I had my kids so young i couldn’t learn to drive i never finished school i was a mess so i thought if i just pack my bags and run every thing would be ok but three weeks went by and i was horrible. i realized i really love him and i wished i never left now were back together and its like hes different. He says i hurt him really bad when i left and also i took the kids with me i was only 5 min. away but before all this it really seemed like he didn’t care now he says he dont know if it is going to work out because he is afraid I am going to leave him again also he works out of town panting so hes like gone most of the time so how can i save are relationship how can i make him understand i love him more than anything i don’t want to lose him again i cant go threw with it again also how can i make him want me or how should i say it think about me more while hes out of town i just want it to be like it was before i left.