people react differently in bench pressing. some like it...others don't for many reasons due to rotator cuff problems, pec tears, etc. however, i'm a firm believer in benching with a barbell to increase overall size and strength in the chest area. dumbbells are great...as a polishing exercise, but if you want mass and strength stick to the basics.
there are many factors that affect your bench numbers...one being your genetics. some people can bench the world whereas others have to live with benching one quarter of it. no need to be ashamed about it...that's just the way it is. another factor is your eating, sleeping, etc. believe it or not, this affects your bench and whole ouput in any workout. third, you need to review your training program. not overtraining is a key element in ANY gain rather it be in strength or size. technique is of absolute importance in benching and not just from a safety point of view. bodybuilders have different styles from powerlifters, and you need to determine which one suits you the best.
if i can give you one piece of advice, work your rotator cuffs. get them stronger so that you can handle more weight. many times your chest muscles can handle the weight but your shoulders can't thus resulting in injury.
so, to answer your question as to what exercises you should do to increase your bench: i'm sure you're doing all of them now. no secrets in big benching as far as specific exercises go. just watch your shoulders and rotator cuffs as you move up in weight. big bench= time + patience
Be smart....Listen to your body, it's your only reliable source.