Hi Lisalou, welcome here. I am so sorry this has happened to you, to be hurt so badly from someone you trusted and gave your whole self to. I admire you for leaving, I am sure it took a lot of courage and strength to do that.
Your feelings of "feeling like a weight has been lifted and you can breathe" all good stuff. It is amazing when we have that space to breathe, to be free, to choose our own path. And yes, mixed feelings come with that..feeling scared, alone, and thinking "Oh my gosh, what have I done?"
My first thought is "are you safe?" Are you in a place where you are safe, away from him? Are your children safe? If he has never hit you before, once you leave there is a chance that the ABUSER can become violent. I would suggest calling your local Domestic Violence Center or even a National Hotline. You can Google it and find one in your country, state, etc. They offer free support, they offer counseling, they have legal advice and practical tips on what to do next. They also have support groups and in some countries, options for safe housing until you can get back on your feet and feel stronger.
I know you may feel like you don't have any family or friends. Even if you have one person that you can talk to or even trust, call them. If you trust them (and I would suggest someone who isn't friends or family of your partner), tell them what is happening. When I told my abusive ex-husband that I wanted a divorce, I told my sister everything. She and I had been close on and off, but we always had each other's back. Even things my ex said..I let someone know because I didn't trust him anymore to not do something desperate and hurt me. My ex never hit me..but the signs of potential violence presented themselves and I was nervous. The name calling, the yelling, the threats..OMG..it was stuff that I never dreamed he would say to me and he did. There is a very strong chance of things getting worse now that you are free.
Please don't hate yourself. I know your mental health is probably not great right now, but know that you are a strong, smart, person who just did a really tough thing. You left an unhealthy relationship and that is HUGE. It is so difficult when being abused.
If you can, focus on you and your children. If you have to talk to your partner..don't. He may try and contact you, he may think you are "bluffing" and this will blow over "once you come to your senses". He may beg to have you back, he may say he is sorry, that he will change, that he loves you and you are the best thing that he has ever had in his life, he will promise never to hurt you again, just give him one more chance". He may cry, he may threaten to commit suicide.
Many women go back to the ABUSER because they fall into this trap that the ABUSER sets. They tell you everything you want to hear and because you love them..you go back. AND IT IS WORSE. Be prepared for this. If you don't go back, he will try many more tactics. He may threaten to hurt your kids or take them from you calling you "unfit". He may accuse you of being the abuser.
If you can..block communication with him. He may text and e-mail and post things on social media all to make you miserable. Because to him..you are doing this to him, you are the problem, you are the one who needs to be punished. My ex threatened me so many times. All tactics to "call my bluff". Block him out for now until you can find the firm ground under your feet. Give yourself time to breathe and figure out your next step.
DON"T listen to him at all. NOT ONE BIT..I promise you he will try and get under your skin. DON"T LET HIM. He will keep abusing you if you give him that chance. NO CONTACT...it is hard..but it is necessary for you to clear your head.
Keep posting Lisalou..there is so much going on in your head and heart..we are here to help in any way we can.