PLEASE STOP USING THE GUN !I would not load one more round into that gun, until that trigger got some attention - Your life could depend upon it.
IMHO, It sounds like someone has adjusted it to a too light, even dangerous, let-off [ or something got caught in the linkage] and it needs to be cleaned/adjusted ASAP, B4 someone gets killed by an inadvertent discharge.
Here's a link, to adjusting the trigger properly:
http://www.varminthunters.com/tech/win70trigger.htmlIf you don't feel confident, in looking into the problem/doing it yourself, please take it to a good Gunsmith - It's an EZ fix.