Gotta gain some weight. Eat more food.
Pick a program, whatever it is and make small adjustments as you go in order to get stronger.
For example: Using 531 - work your normal sets but don't go all out on the last set. Do some joker sets depending on how you feel.
On a 5x5 program, depending on how you run it - add in a few singles after the main work if you feel up to it.
Back off the assistance work for a while and focus on the main lifts.
Take more days off in between sessions or train every day for a few weeks.
Just switch it up and listen to your body. Force your body to do something different.
You're at a point where strength gains are no longer linear and its gonna get tougher. If you're gonna get stronger, you have to adjust. Prepare yourself for a lot of average days of just hitting weight. Not everyday will be magical.
As you keep going, you'll find what works and what doesn't for you as you try different things. You'll find a mainstay, a way you like to train. Then stick to that most of the time and change it up once in a while to keep from getting bored.