couple of things...
A good test to see if your pectorals are too tight is to lay flat on the floor and lock your hands behind your head. Relax your entire upper body and if your elbows are touching the floor then your pecs are not to tight...if they retract toward your center line of your body then they are pulling too heavily and you need to both stretch that area and increase your workout on your upper back.
Side note with working out your back...many times people try to isolate and work on muscle groups that they think are going to fix the problem. That works okay but what you really need to focus on is working your whole back. Rhomboids, rear deltoids, latissimus dorsi, trapezius...by doing so you are basically counteracting. Its neutons law...with ever action there is an equal but opposite reaction, thus, the pulling actions from your back muscles are creating an equal but opposite reaction to the pulling action from the muscles in the front grouping of your muscular structure.
Side note: keep mixing up your workout because the minute your body gets too used to its "routine" then you will stop seeing results.