Each 5x5 (or 3x5) program has its own protocol for when you start stalling like you are doing. One of the more common ones, StrongLifts 5x5, suggests the following protocol for when you stall:
- Attempt the same weight up to 3 times
- After the 3rd time, take 10% off the bar and work back up
- If you hit the wall 3x like this, switch to 3x5 and work your way up
The fact you've been pushing a beginner's 5x5 program for just over a year attests to your fortitude. So please understand that beginner programs are designed for just one thing: to take advantage of your beginner gains.
What's happening is that you are increasing the weight faster than your body can recover. It's inevitable that you will reach that point on a beginner 5x5 program.
My suggestion to you is:
- Take 10% off the bar and switch to a weekly progression for a while until you hit the same barrier (which will be higher)
- Then switch to a monthly progression
A common weekly progression would be Texas Method, or something similar. The bottom line is that for squats you'll be doing one volume day, one light recovery day, and one heavy day. The heavy day you are going for a higher weight than you used on the volume day.
The bottom line is you are 160 lbs and you are squatting more than your body weight. You can add muscle mass, or just try to make the most of your body weight. It really depends on your goals. If your beginner program isn't working anymore after 3 months, it's time to switch things up. If it's still working, then keep at it.