Am I making decent progress on the deadlift?

I am a 36 year old 170 pound 5'8" man man who is strong in the upper body (I can do about 5 sets of 10 pull ups) but weak in the lower body because I have never really done anything other than bodyweight squats and bodyweight lunges. I studied up on how to do proper form for the deadlift. Then I started out with low weight. I was doing about 125 pounds the first time and I did about three sets of 8 reps. The next week (I take a week off in between deadlifting sessions) I did 135 for about three sets of 8 reps. And on the third week (today) I did some warm up sets and then did 135 for one set of 8 and then did 147 for two sets of 8. I have never tried to max out on the deadlift. I just don't want to blow my back out. My lower back and glutes are already tired after these sets I do. I have no clue how much I could do for a max deadlift. I am just trying to start out somewhat slow. So my question is, how soon should I be attempting sets of 200 pounds for 6-8 reps?