Could I be pregnant?

Sadie
Last night my husband and I had unprotected sex, and he came inside of me for the first time. I haven't been on the pill in about six years, but my cycle is very consistent. We have always just used condoms and the pull-out method. We just started TTC last night, and I didn't even realize that I started ovulating yesterday which made my heart skip a beat at the possibility of conceiving. 
Today I'm really crampy which isn't normal after my period, and I won't get my next period for another three weeks. Did any of you out there experience something similar? Could the cramps just be from having sex? We've been together for almost 8 years, and I've never experienced cramping after sex unless it was rougher which last night was not. Or, could I be experiencing cramping from implantation this early? It's very dull but constant.
My chance of conceiving last night was about 9%. 

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