Mom guilt

I just found out I am expecting #3. My oldest daughter will be 11 in November. My son will be 2 in November as well. This baby is due in May so there will be a 2.5 year age gap and I feel nothing but guilt. This baby was planned but I feel like I am taking my sons babyhood away. I just look at him and he’s so innocent and he’s my baby. With this baby coming , he won’t be my baby anymore. With my daughter , I felt like it was easier because she was older and could understand that she was getting a little brother. How do I get over this or through this? Is this normal? I have been non stop crying since finding out and I thought I would be happy but I’ve felt nothing but sadness for my son.