A Flx Avenger SS, Champion Sidewinder, and a DX Viking. I can usually throw around 250'
Simple Answer: Get LIGHTER discs.
Your problem is that you arent getting the disc up to speed (some would say "power" although incorrectly applied.) Until you can get a disc up to speed EVERY DISC will be a meathook; you cant fight the flight dynamics of the disc.
I say this because all of the discs you throw, when pushed to (around) 300' will fly flat and have "understable" (left to right "drift" before the final hooking end : RHBH) tendencies. In short, the problem is YOU. If you are driving 175g discs drop to the 168-170g range... (or as accordingly based on your current weights.)
* It could also be that your discs are not beaten in, but i doubt it.
Long Answer:
Until you have the proper technique (speed, power, snap and form) the discs you are throwing tend to be too much for you. Much like the many posters ahead of me, you are throwing discs that are (still) too advanced for you. The plus with this method is you probably get 30-40' longer than any other disc, but you lose accuracy. you SHOULD disc down and play with more controllable discs, but it would be ok for you to keep trying with your current stack until you reach the 300' mark and really lock in that throw, albeit "improper" so-to-say.
*** BTW - keep working on your snap; snap is probably the most important aspect of throwing after you've mastered the requisite throwing techniques... you can never have too much... your issue is that (even with amazing snap) you are still throwing the disc with insufficient speed (aka "power"). Once you get too much power (disc "flips" and drifts right) you can control the "drift" with snap, you can extend your range greatly, and push slower discs (putters, etc) a lot farther and take advantage of their great control.
hope it helps.
happy discing & welcome to the sport.