Baby 3 and scared

Bethany
Im due February 14th with baby number 3. Kind of freaking out because i have two little boys (recently turn 2 and 3). Im really hoping for a girl this time. My boyfriend is very supportive but he doesnt understand my fear of having another child. My boys are with someone else. Im afraid of so many thing right now. That he may treat the boys differently after this baby is born, that i could have another large child (first was 11.5lbs natural), I'm getting my tubes tied after this one and its a scary thought. No i dont want anymore but what if they come untied, what if my child dies of sids (my older sister died of it and any child i have can as well cuz its genetic). I dont know how to explain this all to him with out him thinking im beong emotional. Oh and he is obsessed with batman and if its a girl he wants to name her harlequinn. Not a bad name but i dont want her named that just cuz of his obsession with batman. I dont know. This time just feels so different because i guess i just dont feel he is fully ready for a kid. (Im 21 hes 24)Ive never been the party type and i love kids. I love my boys, im happy to be pregnant but idk. Help? Advice?