reason for insomnia?

i've been here for 48 days already and i'm still sleeping between 4-7am every night.

went to starbucks the other day and saw this:

"AWAKE - BLACK TEA"

within the first few days i got here, i bought a bag of black tea from teavana. i have been drinking it every night before i go to sleep. i had no idea that the tea would be the reason why i cant sleep at night. normally, i would be knocked out the first 5 minutes i'm in bed. for example, the other night i was ready for bed at 3am, i was wide awake till 7am. retarded. 

i guess i need a different type of tea, like chamomile. 

that should CALM my nerves.