A HR of 150 is high for walking, but at age 22 it is well within a reasonable "aerobic exercise" range, if you are in average physical shape. If you are not, sounds like that is the case, it is still like good to exercise regularly to try to build up some strength and cardio-endurance.
right now moving my heart rate is 150 and my doc said keep it under that... normal heart but 2 months was in the hospital for SVT for near 300bpm
age 22
Your medication is a selective beta blocker (one of the older formulations) and should lower both your HR and BP.
Walking should be fine if you HR is controlled. You didn't give any numbers: HR or age, but for a rough guide I'd say a walking HR in the 100 to 120 should not be any problem. The HR would go higher if climbing a hill or going up stairs, for example.