That's your problem right there bro. I had a problem with strength gains years ago (at around 20yrs old). I feel like I know a little about training and I knew what I was doing should stimulate strength gains. I actually used a tip from a HS coach that use to tell me "when you get set before every play you have to KNOW you are better than the man in front of you, don't just think it... know it!". I started using that with my lifting. I would know before I went to the gym how much I was going to lift before I got there (I used the weight from the week before and added to it appropriately).
e.g. At the time I was working with 275 for 5 x 5's on bp. The next week I would put 285 on the bar and do it. Of course there were some weeks I couldn't get all 5 sets but for about 3 months my bp went up faster than it ever did or has. I started to plateau some at that point but by then I was working out with 335 for 5 x 5's.
I promise you the only thing I did differently was my mental preparation. I just truly believed I was going to lift the weight I had on the bar!
Good luck bro!