How long will this phase last?

Today I experienced something that made me realize I have a new fear. Now, since I have some training and experience with how the mind works this should not be a surprise to me, but it did catch me off guard.
The night JD died I was in town. I had spoken to him on the phone and he was tired but seemed ok. I was going to bring home supper.
About twenty minutes later I discovered I would be quite a bit later than originally thought. I tried to call him again but he didn't answer. Because he carried his phone on him at all times except when it was charging (normally while he slept at night) it was very unusual for him not to answer.
For the next 45 minutes or so I kept trying, I was getting very worried. Then I called our daughter (who lives just a couple hundred feet away) to go check on him. I was afraid he'd fallen and hurt himself since he had a bad back problem and a nerve sometimes pinched and made his leg quit working. To make a long story short she called me back in hysterics. Then I knew something was horribly wrong. I ran (and I cannot run!) to my car a couple of blocks away and raced the eight miles home.
He had died between my first call and the second one twenty minutes later.
I now find that when I call anyone I care about and they do not answer I get that feeling again. I am afraid. I am so very afraid. I'm also afraid if someone calls me and I can't get to the phone immediately.
The "what ifs" are awful.
I do not like this. It is something less than sane. I can't say that for me, at this time, it is totally irrational but it is not good. It is not happy making. I want it to go away.