Don't know what's going on, anyone help?

It's my second day in my ovulation window and I had sex with my husband last night. Went on with my day today and had some cramping but didn't think anything of it. Later on I noticed I was still cramping and I had some bleeding not enough to have to wear a pad but it was dark red/brownish and thick. It's too soon to be pregnant can anyone explain what might be going on?