5 weeks- no symptoms?

When I first found out I was pregnant I was nauseous for a few days. I had sore boobs, hunger and cravings, mild cramping and was so exhausted. This week a lot of those symptoms having increasingly got better. I am 5 weeks today - I haven’t been nauseous for a few days, my boobs don’t hurt, I’ve had insomnia more that exhaustion, not that hungry and now I have a super stiff and sore lower back. I can’t even pick my son up. I did have a pretty extreme panic attack last night and now with the diminishing symptoms and back pain I’m worried I’m going to miscarry. I had nothing like this with my first two pregnancies. Thoughts?