Pregnant right after miscarriage?

Stephenie • 26 years old. Mother of 1 girl 6yrs old plus 3 beautiful step children two boys and a girl. 9, 4, 3.
I posted this same question about 20 mins ago but I can't find it so I'll post again. 
I am really confused and starting to think I'm crazy. I had a very early miscarriage about 3 weeks ago 8/10. My fiancé and I had sex a couple days after without thinking much of it. I had one week without any pregnancy symptoms and I was completely back to normal. Well now I am having very noticeable symptoms again...all of them. Is it possible to conceive right after a miscarriage? And would I be feeling symptoms already?