I feel bad because I'm not happy about my pregnancy yet

I found out 2 weeks ago at my appt to get the nexplanon that I am pregnant with my 5th child. My 4th child turns 1 years old Sunday and I just feel overwhelmed and it all just seems so unreal to me. I know every child is a blessing and I'm lucky enough to be pregnant again and to have all the children I have, but I just feel anxious and unprepared for this pregnancy instead of excited or happy which makes me feel guilty. No matter how many times my husband says everything will be fine I just can't stop feeling overwhelmed, 5 kids in less than 10 years is alot. Thanks for letting me vent.