Neat
All sounds like normal worries to me.
A really good indication that you are doing something "wrong" are cramps or sickness. I know when I've been in a hot shower for too long cause I start to get dizzy and feel a bit sick. I also know when I have done too much exercise cause I get really crampy a few hours later.
Same with sleeping on your back/stomach. Just go with whats comfy. Your body will soon tell you when its time to sleep on your side (LHS is eventually better). I have known people to quasi sleepon on their stomachs til about 30 weeks, and I slept on my back alot even until I was about 35 weeks. Honestly, listen to your body, and hopefully all will be well.

I think that if you get to about 7-8 weeks, your chances of successfully carrying the baby full term are something like 95%. Its really only those first 2-3 weeks where if things are wrong, the baby can abort itself, and you are left with a loss. After this time its far less likely.

Tell your family when you are comfy. My first time I was 7w, the second I was 5w (and lost it at 11w ) and then this time I was 8w. all personal preference.

Congrats, and best wishes