How can I stop doubting myself ?

Force yourself to be brave enough to do the things you feel doubt with in yourself. When you encourage yourself then you will surpass your doubt when you soon realize there was no reason for doubt

I doubt myself all the time. One thing that keeps me going is self-talk. Its the part of my brain that keeps telling me to do the opposite of what the negative part of my brain says. If it says that I will never be regular with exercise and build a stronger body (for example) - I tell myself to just go to the gym/go for a run and not think about the outcome. If I feel like I am not good enough for my job - I tell myself to focus on the smaller tasks at hand and do them better than I normally do. Break things down and find accomplishment in the smaller steps that you completed or the good traits you displayed in the past that tell you that you are capable and right.

Do not ever stop doubting yourself! Many people in this world are afraid to doubt themselves, to second guess, but you should have doubts and fears. To grow as a person, you must be able to overcome these doubts by facing them head on and understanding that failure is a possibility, but so is success. To have doubts is healthy and throughout your life you'll slowly learn that each doubt comes from inexperience and fear. And by having doubts, you're allowed to move forward and create your own courageous story of how you overcame what the world through at you.

By believing in yourself. Belif is key any sort of trust issues, whether its with yourself or not. so yeah