Thank you  for asking Query,
I have read your problem  ,as i understood from Q. you are taking anti-dep Medication
for years ,suddenly you stopped it , suddenly   stopping these 
SSRI medication
is not advisable ,switching  to new anti-dep Medication can do same side effects  like feeling sleepy /
tiredness, &panic attacks.These medications can be stopped   
gradually over 2-4 weeks,tapering the doses by 25%  reduction every 5-days 
 then gradually stop.sudden switching to lexpro without consulting psychiatrist
also do same problem ,as both are different  anti-dep  drug,so i advise you to consult psychiatrist/or gradually stop  
paxil   over2-4 weeks, then start 10 mg Lexpro .Hope u got the answer.
Regards,
Dr M Ibrar