Telling parents.. again.

I was 18 when I got pregnant. Since having my son, I have become a lot more mature and independant, but we are still living under my parents roof to help make our lives a little easier financially. As soon as I told them I was pregnant, they planned this big thing to renovate the basement for us so we could have our own space, and still pay less than what the average cost is for rent. Now almost 2 years later, basement still isn't finished and we're stuck in the main level bedroom with my son, my boyfriend and myself. Baby is just over a year old, and I found out I am expecting again!! Downstairs is pretty customized to our needs (2bd, 1bth, 1 playroom) soo with an extra little munchkin, I don't know how it would work out. Should we just move out? Or can we work with what we have? They're also still kind of controlling in the sense of telling me that my MIL can't comeover more than 4 days/wk once in our own space downstairs.. (shes single, so she comes over a lot to help out & visit baby- which pisses off my mom) I kinda wanna free myself from all their bullshit, but it's just so much cheaper living there & with a 2nd baby, thats more added expenses.. HELP :(