it's not much...if you used a protractor to measure the angle from the floor to bench backrest it should prob be only about 30-35 degrees...use a hammer strength incline bench where you can't screw with the angle to get a good estimate of what it should feel like...the higher you go the more you are using your front delts, which prob hurt because you are using weights you think you should be using for incline bench and working your delts with them...
remember to keep your shoulders back and depressed (like squeezing your shoulder blades together) to get those delts the hell out of the way to let your pecs work
also remember your shoulder joint has an extreme range of motion-your arms can do a lot of shit...but that mobility comes at a price...stability. So don't screw your shoulders up or you're fucked for life
PS train those rear delts too so you don't look like a damn ape...hope i helped