baby num 2........ Just found out (4wks)

So I have a daughter who is 6 yo. my partner has been in her life since she was 6 month's she calls him dad and the bond they have is amazing. Anyway....... We have found out that we are 4 weeks pregnant. My partner looks so happy and excited, but me on the other hand has never felt so scared and worried. I keep thinking about everything how am I gonna cope with the age gap, what am I gonna do about my job, how will I manage again. Am I gonna have a problem pregnancy again, I know I should be jumping for joy. But all I feel is worried and nervous. Has anyone else felt like this, at the no I feel like I'm the only one to be like this. how did you manage with the age gap etc. We have been told that we wouldn't get pregnant as it was taking so long, so this is a massive shock to the system.