I Am A 62 Year Old Man. I Am On

I am a 62 year old man. I am on mild blood pressure medicine. My pressure before the med was about 140/90. It is now around 125/75. My question is, I have been very tired lately, and when I was checking my bp today I found that my pulse was ranging from 49 to 55 bpm. I have been very fatigued for several days, and associated it with some recent weight gain. I weigh 195 and am 5'11". I have noticed in the past that sometimes when I am working and exerting myself, my pulse seems to slow down but beat strong. Can you please give me your opinion on all of this.
Thank you.