Different second pregnancy?

You probably won't get too much advice in the First Time Mums group.
I haven't been pregnant a second time so can't provide you with my own experience but I imagine since it is more familiar being the second time it would be normal to feel different.
At 5 weeks regardless of which pregnancy it is, I think it's normal to not feel "pregnant" yet.

Honestly, I’m pregnant with my second and until around 6 months I could easily forget that I was pregnant! I had no symptoms, didn’t feel pregnant and barely had a bump - also, running around after my 2 year old meant I wasn’t focusing on the pregnancy as much as I did the first time round! I’m now 30 weeks and cannot forget 😂 she moves constantly and I feel massive! Feeling like you’re not pregnant at 5 weeks won’t be a sign that you’re going to miscarry, although there is obviously no guarantee that won’t happen. Just keep positive and try to enjoy not feeling awful for a bit - it’ll come eventually 😂😂 x

I only have 1 so I can’t tell by experience, but my guess is that it just feels different because you have been through it before, the first time everything about it is new, all the sensation, all the feeling, the excitement, the worries, all of it, the second time around, whether you want or not, you might just get in a bit of a “been there done that” state
I really don’t think it has anything to do with a potential miscarriage, don’t worry to much about it, just take each day as it comes

Totally normal! You have a lot more to think about this time around with a baby to take care of :) it’ll go by much faster this time too! You don’t have as much time to focus on your pregnancy symptoms, plus you’ve gone through it once before so you’re not going to notice it as much. At least that’s how it was for me and all of my mom friends with two!

Totally normal. I’m on my 3rd with a 10y and 22mo. You have so much going on that pregnancy takes a back burner.

That's pretty normal. You're probably busier than you were with your first! How you're feeling in that regard has nothing to do with whether the pregnancy will stick or not.