Arguing with Bf about CIO method

We have an almost 3 month old baby girl who he has told me over and over that I should be letting her cry it out, that she shouldn't be so dependant on me, that I'm going to regret it if I spoil her etc etc. I am home 24/7 with her and his other 2 kids while he works 12 hour shifts for 2 weeks at a time. He says the other kids' mom spoiled their oldest child and that is why she is stubborn and has a bad attitude now (she's 6). They let their second child CIO from early on and personally I don't think he is much different. Anyways he is constantly arguing with me that I should let my baby CIO to the point where I'm starting to get upset about it because we've already talked many times about how I feel about that opinion. It is my first baby and I have a very close bond with her. I love my family but she is my everything and it brings me to tears to even think about letting her scream when she needs me. I have read that 5 or 6 months will be an acceptable time to start sleep training and told him I will figure it out then. I don't want her to be a bratty little kid either but I don't feel like doing CIO this early is really the way of accomplishing that. I have nothing against anyone who uses this method with their children, I'm sure one day soon I will have to. I just am trusting my instincts that I don't want to do it yet. I don't want to argue with my boyfriend about it either but he is pretty much trying to start fights with me all the time to try to prove that he is right. Not sure what I am looking for by posting here other than to vent to some people who have more experience on the subject Than I do. Any advice is appreciatedEdit: I am also breastfeeding and unable to pump so you can see why it's hard for me to be away from the baby and why she is so attached to me. via /r/Parenting http://ift.tt/2alxmqb