Single mother 😔

I’m 22 years old I have 3 kids one on way, all my kids have same father. Recently we’ve been going through a rough patch in relationships, he’s finally told me he’s unhappy. We been knowing each other since we were 16&18 teen been dating for 5 years. Every relationship have problems etc. Now, I feel we’ve out grew each other in so many ways it’s not like when we where younger love done been tested loyalty and honesty has been broke and tested. I’ve tried to make it work fix things and hold on to my family because nobody wants to start over. I’ve never been alone I’ve always had him. He’s cheated multiple times but I forgave and fought harder as ever for us but I don’t understand how can someone fall out of love with someone you supposedly love and have kids with. I’ve always been the type that want her family an not a stranger. How do I start over how do I explain to my kids it’s just gone be us now. I’m very heart cause it breaks my heart to rip away my family. He doesn’t love me anymore or care about me. I really don’t know how bad this will hurt me but it hurts now and I feel like i failed at something and I’m not gone ever in life find happiness. Especially since I’ll be a single mom with 4 kids. I don’t know I’m just venting and upset and hurt.