husband wants a baby but I don't.

Here is a dilemma.  I'm 41yo, have a son 17yo from previous relationship. Recently got married second time and my DH now tells me he wants kids. We did discuss the matter before the wedding and both were equally easy about it  - 'whatever happens '.  Earlier this year I miscarried on 5 weeks. After our latest argument I realised that I enjoy my free life and I don't really want to be bound by a child again. Although I never had a burning desire to have a baby and my first one was rather ' an altruistic gift' to my first husband as he wanted  kids ( I was young and naive, he was emotionally abusive and marriage fell apart).  My son is the dearest person in my life and though it was never easy with him , I'm so happy and proud of my motherhood. Now, I love my DH and feel it is cruel to not give him the opportunity to be a father, but I can't help feeling that the situation repeats itself.  I know if I had a kid agin  I would love him/ her to bits, but I love my freedom , easy and quiet life, to which I was so looking forward to for the last 17 years... your thoughts ?