i am going to try to say this as "gently" as possible. yes, you need to see a counselor or therapist. someone needs to help you see past yourself. yes, your HUSBAND has every right to veto a third child. quite simply, there is no reason except "I WANT" for you to have another baby. what does that tell you? if one of your kids wanted a 5000 calorie sundae with the works, and when you asked for a good reason, all they could come up with was, "because it's what I WANT!", would you give it to them? just because they wanted it?? life isn't just about what one wants.
think about someone else. and be honest. are your kids suffering because of your "depression"? god forbid, do they know the reason for it? what about your husband? how do you think he feels when his reasons are being completely ignored? that he and the kids aren't good enough to "make" you happy? last what about the "non existent" baby that you are so in love with and are spending so much emotional energy on? that's an awful lot of responsibility to place on one baby's shoulders. it's sole reason for being, would be to "make" mom happy.
seems to me you are pretty much slapping your family in the face on every level.
okay i am sorry if that was harsh. please see someone for some help, if you can't get past this. you are really hurting your family, i am sure. at some point you have forgotten to appreciate and cherish what you have been given. if you can't get that back, it's okay to need help. no baby will ever "make" you happy if you aren't happy with yourself. we ALL feel the instinct to have babies. but babies don't make us happy. no outside source can MAKE you happy. that has to come from you and dear, trust me when i say i mean this in the nicest friendliest way possible, somehow you have GOT to realize this, for your family's sake. i know a lot will disagree with me and probably call me out for my opinion...it's the truth as i see it. you have been so very blessed. is it worth throwing all that under the bus just to get what you want??