Sounds like you have been suffering from Generalised Anxiety Disorder since past 18 years. I would suggest you to take a structured therapy approach which involves a lot of breathing exercises that would calm you down, along with different therapeutic approaches we use for anxiety and panic attacks. Since you are telling you are getting dysfunctional I would suggest you take help at the earliest. For the time being please listen to some audio clips on relaxation that would calm you down. Also read our articles on Anxiety at www.seraniti.com. Hope it helped. Thank you