There could be one or several things that may be a little off.
Several questions/things for you to look at.
Are you shooting quality arrows or did you buy the least expensive arrows to save money? A good arrow makes shooting broadheads much much easier. It's hard to get good broadhead flight if your arrows are crooked, weight is off from one to the next, and if the spine of the arrow is inconsistent from one to the other.
What spine are the arrows and how long are they cut?
Are your fletchings making contact with your rest or riser?
Did you spin your arrows with broadheads installed to make sure they are perfectly in line with each other? I'm not talking about aligning the blades with the vanes. I'm talking about making sure the broadhead is perfectly straight in line with the arrow shaft.
Have you tried any tuning methods yourself or did you have someone at a shop tune your bow for you. Every one needs to know how to tune a bow if they are going to shoot one. It's like being a guitarist and not knowing how to tune a guitar. Even though we offer paper tuning at the store it isn't going to be perfect if you don't know how to fine tune yourself.
Do you have any cam lean in your bow while it's at rest?
Are the cams in sync with each other?
Are you shooting with a completely relaxed, neutral grip or are you holding the bow or forcing your hand open?
And finally,
READ THIS........
http://www.eastonarchery.com/img/downloads/software/tuning_guide.pdf
Oh yeah, one more thing. If you decide to shoot a mechanical because of this then you are doing nothing to help yourself. You're only putting a band aid on a problem that still exists.
On another note....... I'm sure it will get brought up here again so I'll go ahead and address it now.
I don't know who it was and don't care to argue about it so if it was anyone that's posted on this thread don't get your feathers ruffled but someone on another tuning thread a while back commented about pro shops setting up a bow by "eyeballing" them instead of using lasers to set center shot and level the arrow perfectly. These lasers do absolutely nothing what so ever to make sure your bow is tuned nor do they get the bow close. Sure the look cool and the ill informed customer thinks they are getting some kind of "super tune" but they are getting duped. How many times do you think it takes for a pro shop to set up a specific bow model before they get it figured out?
There are a very few bows that have the ability to shoot true center shot after being tuned. Every bow exhibits side torque due to the cables being pulled off center to allow for clearance for the fletchings. Not only does this cause side torque but it also causes cam lean at full draw. Couple this with imperfect humans holding the bow and 99.9% of all bows out there will tune left of center (for a right handed shooter) and the majority of them will tune nock high.
Bottom line is don't get taken by some pro shop breaking out all of these fancy gadgets and think you are getting something you aren't.