Interesting on the MIL, because I think if I was having these symptoms and they were caused by the MIL moving in, I would force that situation to change. Health trumps all, but we all have our own situations.
For me, I was always a "worry wort". I stressed about finances, career, kids being given fair treatment on the soccer/basketball team, how others might judge me/us, which car was the right car for me to buy, and all of that stuff - but it never affected me physically.
For me, I presume it was this sequence that sent me over the edge:
Dec 7th: My company tells the entire firm that they will be closing in 3 weeks. Merry Christmas ...
Dec 14th: We are waiting to find out which lucky few will be able to stick around a few more months to help wind down. I am not one of them.
Dec 20th: Firm finally tells us what the severance package will be (turns out there is no severance, but we get a hefty end of year bonus)
Mid-January: I am now interviewing with 7-8 different firms, dealing with grueling interviews that last up to 6 hours. This same week, my dad goes to ER for emergency surgery.
One day after this brutal week, I have a panic attack in the shower, home alone, and think I am having a heart attack.
I have been overly sensitized every since. I hear every heart beat, feel every tick of pain or tightness in my muscles. Aches in my calves are obviously life threatening blood clots. I am afraid to go jogging or go skiing. Afraid to shovel snow. Doctors have done tests and tell me it's just anxiety, but doubt creeps in.
It's like a switch was turned on, randomly, and I can't switch it off. My wife is not sympathetic, and is more annoyed than anything. I also can't bring myself to get it on in the sack, as trying to do so now causes me palpitations. Brutal.