Mixed emotions

Last month I decided to have my IUD removed. I was having a lot of terrible side effects from it. My SO and I decided together that we wanted kids soon so I didn't go on birth control when my IUD was removed. We agreed that we weren't trying to conceive but we weren't really preventing either. 5 weeks later I get a BFP. Now I totally have mixed emotions. I was expecting it to take a few months to get pregnant. I feel like I should be more excited. My SO is stoked and keeps giving me these big ass grins and touching my tummy. Why aren't I more excited? I'm 31, have a great SO, a great job, and we just bought a house. Hopefully, it's just shock and I'll come around soon.