marriage?

Me and my husband have been together for 5 and half years, only married for 6 months. We have a 3 year old daughter. Over the years my husband seems to have changed so much, he's always negative, he's never romantic, never spontaneous, never happy or complimentary, he doesn't want to spend time with me, he does very little with our daughter and he always wants to act and be like one of the guys cos none of his friends are married or have kids yet. I don't know how I feel about him anymore. But I feel like I could never leave him because I wouldn't want it to affect our daughter in anyway. I feel a little trapped. Iv spoke to him about how I feel and he then says splitting up is the last thing he wants, he admits he has changed and doesn't make an effort anymore and promises to do so in future, this lasts a couple of days then he is back to his old self. I don't know what more to do but I don't feel like I have the guts to leave him. Also from may I have been suffering from depression, I'm not sure if been stuck in this relationship is causing the depression or if the depression is causing me to question the relationship ?