Very conflicted :/

My boyfriend and I have been together for 4 years, he has a wonderful beautiful amazing son from a previous relationship and the two of them mean the world to me. I love children and it's actually been depressing me lately being with him and his son because I want so badly to have a child of OUR own. He has 50/50 custody with the child's mother so he is only at our house 50% of the time. Plus i just have this feeling where I need more, I know what I mean to the child but I also know I am not his mother although I treat and care for him as If he was my own. We've talked about TTC but I'm waiting for my new job to start (hopefully within the next month) as currently I have little income, and our home is only a 2 bedroom although our lease is up in February and we are looking and willing not to renew our lease so we could hopefully find a little bit bigger home. I've just been feeling very empty lately and remotely unhappy, but evey time I see I new baby I feel the sadness lift and can feel my face light up with joy! I would love to start TTC but I still feel conflicted due to our house and not having started my job yet(I'm a COTA/L btw, so I will have a satisfying income. ) Any advise here would be so greatly appreciated! I just feel very stuck! Thank you in advance :)