I'm sorry, I didn't mean to sound harsh.
I guess I'm just astounded that this sister has spent the last thirteen years effectively on her own, bar 15 days, and she's questioning her self?
I think Sr Se7en has good ideas, go introduce yourself and your children to your inlaws, invite them to meet your parents etc.
Also are there any drug helplines/centres available where you are, where you can get advice on this qat addiction of your husbands, can you speak to your imam, and once you've met your in laws perhaps speak to them of your concerns, altho to be honest, dont go in with 'Hi, I'm your other daughter in law, these are your other grandkids, and btw, your son has a severe drug addiction which is driving me insane...'
But then you've spent a long time with this in your life, so you would know better how to approach your husbands parents about the issue.
As for wife number one, be nice to her whenever you meet, your husbands treatment of you both has been severely lacking in anything even approaching respect and love. You two are not adversaries.
Out of curiosity, why did you agree to marry your husband secretly? This always really astounds me, you're a wife, Islamically and legally recognised (I'm assuming you reside in a country where your status as a legal spouse is recognised), why would you wish to hide it from the world in direct conflict of your own God given rights?