need to add strength

ok , mondays.... hahah i hate them!
 i workout weekdays take weekends off  , like every guy i want the nice strong chest with big attractive pecs! hahaha ,  ive been working out a year , dedicated , alittle sloppy for  a few months as far as dieting and not focusing enuf on other muscles but  didcated none the less and even more focussed now , ive gained size whihc is the goal , but my strength is pethedic , on a good day i lift something im proud of , the nextw eek i may be weaker then usual , mondays my chest day and im always weak and lazy during it ,
my problems are my shoulders always get sooooooo tired before the rest of my chest or tris so i cant lift as heavy or go aslong as i feel i could if the shoulders werent so lazy.
anyway , should i lift heavy for abit? size goal is my objective , but for chest and tris , should i maybe do 5x5? or 3x4-6? with as heavy as i can go? cuz i need some strength here!
also on thing , with these rep ranges..should i be able to get to 4 , 5  or 6 reps without a spot , or if i get to lets say 2 or 3 on my own and get spotted for the rest does that count?
thanks

the post was confusing.  You say size is your objective but you want strength?  You can have both but usually there is more of a focus towards one or the other.

Also, the "my shoulders are tired" to me says you just need a more balanced workout.  Consistency should take care of your fatigue but being lazy, thats all mental and if you want to get big/strong you need to get that out of your head right now.

I love chest days.  :)  if you need motivation why not start off mondays with legs, chest on tuesday?

good luck.  STAY MOTIVATED.  you can have that body you want if you work hard enough

age: 24
height: 6'4"
weight: 217lbs
bf% 15
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currently attempting first bulk