Wiretapping Help

TL/DR at bottom.
Throwaway account for privacy. I (27) am in a difficult situation. My girlfriend (29) and I have been together for 10 years. We had to live with my family due to stupid financial mistakes when we were younger and we have a child together during that time. She shortly after his birth developed a drinking problem which she has been working on tremendously (minor set backs here and there as expected) but she has been doing very good lately. The problem is between her and my mother because of what happened. I already know my mother is a narcissistic control freak and it got to a point where my girlfriend was kicked out of the house because the 2 of them couldn’t be together anymore. So I worked really hard picking up gig work and cutting all unnecessary expenses and we were able to clean up enough finances to finally get our own place a few months ago. We have not had my mother over because the tension between the 2 and because I found out from my mother who one day stupidly bragged to me that she knows everything going on. When my girlfriend was kicked out my grandmother took her in and shortly after that my mother bragged to me that she knows everything that goes on because she planted a bug in my grandmothers house. I made my grandmother aware and she resorted to allowing it to happen, and for months all our conversations had to be whispers in ears. We did not want my mother over for fear she would do that to our new apartment. Well the other day we got home and found my mothers notebook in our bedroom which has never been here as my mother has never been here per our wishes. Also found out she rummaged through my girlfriend’s medications because the last page of the notebook had all the medication names and dosages of everything she takes. So we frantically started searching the house and found a bug here as well stuck to the back of the fridge. I asked my grandmother if she given my mother the spare key which she said no. So either she is lying or my mother secretly grabbed the key and made a copy because I still found the original spare at my grandmothers house. I changed the lock that very night for our peace of mind. I’m not sure exactly what to do besides confront her about it and see what she has to say but I also want to get some sort of hard stop to this legally because we are now uncomfortable in our own home because we want to believe there was more than 1 bug but can’t find another one as of yet. My state (MA) has very strict laws about eavesdropping/wiretapping so I definitely want to go the legal route but not sure where to start (obviously a lawyer is where to go, but I’d like more of a heads of before I have to start writing a check for one) please help with any advice.

TL/DR: Found audio recording device in my home planted by someone with no permission to enter the house as they were never wanted on the property and were never given a key. Location: Massachusetts