I'm so depressed lately

Because I want to be a mom so bad. It's all I can think about and it's making me so depressed where all I want to do it cry. I don't know what to do. My bf doesn't want kids yet and it's literally just breaking my heart. It's like physically bothering me. I don't know what to do about it. How to stop it. I feel like those dogs that get depressed when they get fixed before they have had a litter of puppies. I have been around kids,since I have 7 nieces and nephews, since I was 9 years old and instantly started baby sitting infants 3 weeks old (with supervision until I was about 11) and I know I'd be such a great mom. I just feel so empty and depressed. I know it's not anything else. My body and my heart is telling me I want to be a mother more than anything. It's all I've ever wanted to be since I was young taking care of my dolls like my children. I just don't know what to do. Could anyone help give me advice.