I'm torn between moving on but staying for my children

I have 3 children. 1 boy 2 girls. My girls father and I split 6 months ago. Since then we do a joint custody agreement. 1 week with him 1 week with me and it's been incredibly hard on the girls. They are used to mama. Within this 6 months I've recently met a guy. I adore him. Hes so grown up so kind I feel safe with him. I really wanna see where it goes but then heres my ex wanting to get back together. I just feel so torn in this situation. If I stay with my girls dad I gotta worry about my son feeling left out but I can have my girls all the time. If I move on with this other guy I'm loosing my girls every other week . If I stay I can call the shots with my kids if I go I loose everything. I feel like if I pick this guy I'm picking him over my children. I dont know what to do it's been a emotional battle past week. I feel so trapped.