Don't forget, as well as this all being a normal reaction, you will have hormones to contend with too!!
I was pregnant before all my friends, and I after a few weeks it suddenly hit me that I had never changed a nappy. I was really fixated on the fact I wouldn't be able to do it (in retrospect, I should have just brought a doll and a nappy, would have saved me weeks of hormonal irrational stressing). I watched YouTube videos, I googled it and, in fairness, I logically knew it wouldn't be that difficult, I think I was just so stressed about the whole entire thing that my brain had to focus on one single point.
I spent a fortune (I still wince thinking about it now) on pregnancy and baby books and read everything I could. I did chill out towards the end but I can honestly say I never once looked at those books once DS was born and had no issues getting to grips with nappies.
Very few people know how to be a mum before they are one, and I suspect everyone panics, even if all your friends had had a baby first - it's still different when you know that baby is going to be your responsibility.
As PP said, if you can tell your mum now, then do. I had a strained relationship with my mum prior to DS but she was my rock through pregnancy and we have been close ever since. She was there with the answers to my never ending list of panicky questions and she never once minimised my concerns or made me feel silly.
Don't panic OP, you can do this! And congratulations!!