TMI

I have had normal periods & I'm not on birth control. My period ended 10 days ago on the 18th and last night I noticed a little spotting and today its a lot of blood, and I'm having a lot of dull pains in my abdomen. I haven't had sex in over a week & I'm pretty sure I can't be pregnant as I've always used condoms. I know nobody here is a doctor, just hoping for some advice on if this might be serious or just nothing.