How would this dynamic make you feel?

6m ago I moved into my boyfriends home when we had our son, he’s buying so I felt more comfortable raising a child in his home as too where I was living with several people stacked on each other. Well fast forward too now I’m still here & my boyfriend has never made it an requirement for me too pay anything. Well the other night he disclosed to me that his mom handles the water/electric he pays mortgage + land taxes they have this type of set up because mom is on the deed & can drop in when ever for how ever long she pleases (mom also doesn’t have a home of her owns she does live ins so she’s about like me just likes the security in knowing she has a home too come back too) well I’m going back too work & I feel like I should be paying at least the electric+water both bills alone are only $130 an thats for all 3 of us. Would I be wrong to tell his mom she doesn’t have to worry about those bills? This is not me saying she not welcome whenever I just feel it’s not her job especially when I’ve been allowed to stay here bill free they’ve never made me feel like I couldn’t be here or like I was burden I just want too contribute