TTC am I being stupid???

I’m trying to get pregnant but it’s not working. So lately after he finishes in me, I lay with my feet up the wall to keep it all in my vagina for like 10 minutes. Does that even work. Do I need to “marinate” it in me? Or should it happen as soon as he cums. I feel dumb but I just want it to be in me longer just in case. I just want a baby