I get a lot of those symptoms too.
- I get headaches and a sore throat/lump in the throat when I'm stressed.
- I get pains all over my torso when I'm anxious, especially the left side of my chest which is always scary
- and of course heart racing
My main symptom is nausea and when I am heading into panic attack territory I have shortness of breath.
I don't know exactly what you mean by "feeling like sometimes im drifting in and out of my own existence" - but I might get something similar due to depression? I tend to zone out a lot, then come back to my senses a bit. I also have a bad short term memory usually because of my anxiety. Not sure if this is the same thing as you or not but everyone gets different symptoms with different severity levels so you're probably not strange in that regard don't worry lol
and I know how it can affect your sex life too :S sex = heart racing = brain thinking you're having an anxiety symptom or heading into a panic attack = making your body freak out and actually have a real panic attack.
I was quite happy and confident too when it really hit me bad, it seems like it is common for confident happy people to suddenly get hit by this thing. For me my doctor and psychologist think it happened due to having poor coping techniques and failing to work through my problems and everything just built up until my body finally caved in under the pressure of all the unresolved stuff. Not always 100% if that's true but it makes sense to me and could easily totally be it.
Have you spoken to your doctor or a counsellor or anyone about your anxiety? If not, give it a go, ask any questions you have. I find that the more I know about anxiety and my symptoms and how my body reacts to it all actually helps me to manage it much better than I used to when I was first diagnosed and knew nothing about it.