Hello Rosa Maria,
Welcome to the forum.
Feeling isolated is damaging to anyone's self esteem and children are no different. I am sure that you are right when you say that his esteem has been affected. I will be happy to help you with how to start.
Firstly and most importantly, Gather your evidence for how feels? What does he say about how he feels?
Looking for things like. What he feels inside? What others say to him? How that makes him feel? How he'd like to be?. etc.
These are only suggestions. It would be best if this type of fact finding comes from casual conversation from him rather than direct questions on the spot.
Words he uses form the set up statements. Post back what he says and if you need help I will show you how to form a statement and where to take it. If he doesn't really talk easily then don't worry, we have to be more creative and use some other options. Let me know.
There is likely to be many layers of feelings. Tapping is an excellent gentle way to rebalance at each stage.
Do you tap? If so, does he watch, see the results? Is he interested?
What are his interests? Knowing this type of info helps me to give you ideas about how to inspire his interest to feel differently.
Surrogate tapping is another option which can help.
Reading some of my other posts about tapping for all the family and surrogate tapping and leading by example on this forum may also be good for you to read. If you can't locate them just let me know.
I would love to think that your son is interested in the possibility of feeling different. Perhaps he may be interested in taking a look at the Zapping Zone on my website below which gives a broad idea of things that Children and Young People use EFT for. I am due to post some more children's feedback on there very shortly.
Hope this is enough to get you started.
Looking foraard to hearing back
Christine