Can I go to the gym and lift weights, since I have high blood pressure (150/90)? I am 31 years old, 6-1, 230lbs.

No. First take care of your blood pressure. Aerobic exercise can help your blood pressure as can dietary changes. Lifting weights can transiently raise your blood pressure to dangerous levels. Also high BP can thicken the heart muscle which is worsened by lifting weights.
Light weights. As you're exercising with weights, the struggle of pushing or pulling heavy weights can spike your blood pressure acutely, which could lead to problems if your blood pressure is not adequately controlled. Exercising with light weights along with aerobic exercise can help to lower your blood pressure in the long term. You should exercise, but with prudence.
Yes. You can and should continue to exercise but obviously will need to treat your blood pressure as well. One way to assess your blood pressure response to exercise would be an exercise treadmill stress test during which your blood pressure response will be monitored. That could be done while you are on medication to confirm that your blood pressure remains well controlled even with strenuous activity.