First of all, if I were you, I would talk to your husband about the mother in law issues and just tell him how you feel and tell him that he needs to lay it out for his mother. Second, sex only CAN induce labor if you are already about to go (per my midwife). And you will most likely know when your water breaks. I hear that it can 'trickle' out, but mine gushed, a lot, for about an hour.
I think you are being a normal mom. Also most women don't have their water break until they are in active labor. Having sex isn't going to break your water it will only induce contractions. Also You are still early, every day or week or baby stay in the healthier it will be, also you baby will come when they are ready.