negative family

so my husband and I have been married 6 years and have 3 kids. we live across the country from both of our families due to military so we do it all ourselves (not complaining, I love our life). I told my mom and sister that we are trying for another baby and just got negative comments... I am a stay at home mom and student. our kids are happy healthy kids (hyper and crazy but what 5, 4, and 1 yr old isnt?) and I have said sense our first that we want 4kids close together. I feel hurt and confused. I love my babies and want to have our last while I can still be home and take care of it myself like I have with my other 3(after getting my degree i'm going back to work). I feel alone, other than my husband of course, but he doesn't understand because I am very close to my family, especially my mom and sister, and he isn't like that with his. I've just been so down since telling them. i haven't changed my mind and won't regardless of what they say. ii'm still so excited about trying for another baby, but I feel so sad and down. I thought they would be supportive and now I don't even want to tell them when it actually happens, or even talk to them at all right now..... any advice?