This type of program has survived and produced results for going-on 80 years. It works just fine, unless you screw it up.
For context, what's your height, weight, general bodyfat, and current goal?
Based on what you wrote, you're not actually doing Park's version of 5x5. He suggested "5x5", but the first two sets are warm-ups with progressively heavier weight and the last three sets use the working weight with a full 3-5 minutes rest between sets. This article, taken straight from the book Reg Park wrote, explains his plan.
There are a few different ways to run a "5x5 program" and each one has its own pros/cons and twists on programming. Understand what you're doing or you'll spin your wheels.
This is worth repeating. Shocker to many new lifters, but not every effective program needs to work off a 1RM percentage. Base the weight off your actual performance. In Park's program, specifically, he advocated never hitting muscular failure. So you should always be able to get your 5 reps or, if you can't, you shouldn't fail mid-rep so always keep one in the tank.