I just tried a yoga for relaxation class on Monday and it was amazing. No impact so not an exercise class, but I've not felt that relaxed in a while. When I found myself in a stressful situation afterwards, I used the breathing techniques and actually felt more calm than I expected.
As for people that stress you out, you might just have to tell them you'll have to speak with them once your son is safely here. Some people just don't really get it, but if they are stressing you out, you have every right to say something to them if you think you can.