Anxiety / spaced out

Hey everyone,
(please excuse my grammar)
I've been a sufferer of Anxiety for around 5 years now.
I'm 24/m/uk and lead a perfectly healthy lifestyle. I work full-time and have lots of family and friends.
It all began when I was 19. I woke up one morning feeling completely spaced out. This obviously brought on anxiety and stress as I didn't know what was happening. Ever since then this feeling of being spaced out has played on my mind everyday ever since, obviously bringing on anxiety and depression.
Over the past 3 weeks I have had the same symptoms as I did when I was 19.
Symptoms:

Spaced out feeling
Heavy heart beat (almost like someone is holding my heart and slightly squeezing)
Muscle tension in legs
Feeling angry/annoyed
Nausea
Questioning reality
I haven't had any suicidal thoughts as of yet but have the feeling that being dead would be a hell of alot easier than suffering from this for the rest of my life.

Now I know these thoughts are stupid and I shouldn't be thinking/feeling like this but I am and am finding hard to stop feeling this way.

I'm basically scared as if I'm thinking like this after 3 weeks what will I be like after a month/2months.

I have been to the doctors who have prescrived me a mild anti-depressant. I know there is no cure for Anxiety but I'd just like any advice on how to manage/deal with these kind of thoughts/physical symptoms.

Many thanks

:)