How do I go about being more confident in myself to provide for me and my children myself?

You have taken the first step by acknowledging that these things are not true and that you are capable, which is terrific! You are also seeking out help which speaks volumes to you readiness to make change happen in your life. Having said that, these situations are never easy, especially when there are children involved.

You can start becoming more confident through the use of affirmations and asking the question of what proof do you have that what is being said about you (or what you are thinking) is true. Noticing maladaptive thoughts is the first step but then also questioning if they are valid. Once these processes become habit, your kids will notice as well (as kids notice everything right?). 

Think about even setting quotes and things that are true about yourself as your phone background or lock screen, on your computer, or even on sticky notes in your car. Repeat these things to yourself as you walk through your day. Also, it can be helpful to carry a notebook around with you to record times when you are speaking negatively to yourself and how you counteracted what you are telling yourself with a truth. 

Reading affirming and uplifting books can also help (if you enjoy reading). Sometimes making a playlist of empowering songs to listen to as you are going about your day can assist as well. Small steps towards being able to easier address doubts, fears, and lies you tell yourself. 

One more thing you can do to incorporate your kiddos is to create fun ways to build each other up. You can make it a game with them that when one negative thing is said they have to follow it up with a positive. Have them participate in the process, not only does this make it easier for you to not be doing it alone, but also brings you and your kids closer together. 

Hope some of these things are helpful! Working through situations and your internal narrative in therapy will assist you as well. It makes it so much harder when you are also hearing someone on the outside saying things to contribute to your doubts and fears. It's not impossible to overcome, just not always easy but you can do it!