Why do I get anxiety?

Hey guys my name is pablo and im 23 years old. I want to know why this just started to happen to me with anxiety attacks. I never had this problem till now and I need advise. I wont lie but back then I was drug addic and alcoholic. I quit drugs about two months ago and stopped drinking for awhile because I was noticing that this attack was getting to me which is anxiety. Now I recently stayed sober and not done nothing. Im a person that dont sleep at night and will usually crash out at 6 in the morning. Doing that after I was getting to a point that is getting to me while being sober and trying to fall asleep at six in the morning. I close my eyes and feel tired when out of the blue the attack come and gives me anxiety. I talked to my doc and he said hes not sure what it could be why this is happening. They gave me pills to feel relaxed and will need to go back to check my blood results. Please can anybody help and maybe know wats happenin thanks