I need some advice...?

I have this problem that seems really ridiculous to people... but it is affecting me really bad. I have a problem concentrating on my thoughts, such as breathing. I know your body breathes on its own...but i always think of when to exhale and what to inhale..and i start to panic. I went to see a doctor..and they put me on meds (anti depressant) because of how depressed i was from it. The meds helped for a few months...but in no time, my problems started to come back.I always feel so down..and i just never feel like doing anything because of this problem. I really feel as if this issue will just stay with me for the rest of my life. I just feel really depressed and want to know if their is anything i could do to stop this. Any advice will be helpful..thank you.