I usually unstring my stickbows when not in use, but no longer than youve had it i doubt leaving it strung would have hurt it. Traditional bows are harder to shoot, your form has to be very consistent, im guessing some how youve changed something in your preshot you dont even realize, either that or you arent following thru. Its really easy to get off your game, especially if you pick the bow up and start shooting it well right off the bat, then you get to thinking "heck this is easy" and then you will stop doing some of the things you were doing before because you think youve got it down pat. Its happened to me before too. Move in a little closer and take your time, notice what you are doing when things work and what you stopped doing when things dont. Also plenty of great books out there on stickbow shooting, one of those might help diagnose the problem too.