Ive been working out for a long time now and lately for the past month or so some of my exercises just arent going up in weight anymore. Just as an example i started my flat bench with 45 pound dumbells and within like a month or so i went up to 65 pound dumbells and for the past 4 or 5 weeks im stuck there. The weight just wont go up anymore. I do 3 sets at 6-8 reps. Any suggestions guys? Thanks.