Poolside

I am 59, and have been taking Atenolol 25mg for about 15 years to treat my hypertension. I originally was taking 50mg, but a few years ago my doctor cut me back, and my BP has been in the 120/70-ish range while on the meds.
Recently my left shoulder starting hurting me, and I attributed the pain to tendonitis or some sort of inflamation of the joint. I have had this shoulder pain from time to time, so I took it in stride treating it with Advil or Aleve. Then something new started with a very slight tingle on the top of my hand. This was a symptom that caused me concern, because I'm thinking it could be a cardiac issue. I went to my regular doctor, and he took my BP (120/70), and told me the sensations I'm experiencing with my arm and hand are probably related to the shoulder problem. Okay, I'm good with that, because who wants to hear the it could be a heart problem.
One week passes, and I'm getting no improvement. As a matter of fact last Saturday morning, while out doing food shopping, I got very light headed to the point of almost passing out. This really scared me, so I made an appointment to see my cardiologist. I saw him last Tuesday, and when he took my BP it was 150/90. I told me it was probably because I have been worring about it, and was nervous about seeing him. He also did an EKG, and saw nothing out of the ordinary, execpt a right bundle branch block, which I've had since birth. He scheduled a Thallium stress test, and an Echo Cardiogram for this next Wednesday.
The rest of Tuesday I felt pretty good, but Wednesday I felt kind of funky. Then Wednesday night (last night) I had a couple of light headed episodes that started me worring, so I took my BP, which was 162/90.
This morning I doubled up on the Atenolol 25mg, and felt a little better. Later in the afternoon I stopped by a CVS and used a BP machine they have, because I was curious what my BP would be. It was 164/83.
My question is...If my BP was controlled for all those years, what would cause this sudden rise? Are the sensations I am experiencing in my left hand, and the pain in my shoulder related to the sudden rise?
I have had no chest pains, and only a couple of rapid heartbeat instances. I do have flutters once in a while, so that's not out of the ordinary.

I have another appointment with the cardiologist tomorrow, but I'm trying to get some other input to set my mind at ease.

Thanks....