mixed feelings creeping up

so i started a new job. And its the job i’ve alwasy wanted. And in the beginning i was feeling so lucky and so fullfilled. And i talked about how amazing it is etc.
and now i noticed that i don’t anymore. I don’t exactly think its a pain but i noticed that i don’t give 100% effort to my work.
to clear up i work with teenagers who have a hard time to find their place in our society. meaning they have more difficulties to find a job etc.

i noticed that i have lots of negative feelings and thoughts about myself.
things like: I’m not smart enough, I don’t have the knowledge, they other one can to it better, the only good thing i have here is that the teenagers like me, I don’t know how things work and therefore i should be ashamed.

I feel inadequate.

the funny thing is that they offered me a full time job. Now i^’m doing an internship.

and my boss is looking for a new person to fill the internship position. And everytime someone comes in for an interview i notice how i get all panicky and shitty, because i think they will be better than me. The other will like her more.

i notice i have to work it out. There is a lot of insecurity going on here.