Spotting during fertile window...

I spotted for like four days during my fertile window. Would anyone think this could be due to a possible pregnancy?? This would be baby #4 for me...and I havent been pregnant in four years so I dont really remember how I felt when I was. My period is due Thursday and I have been experiencing cramps and minor back aches. As we speak I am feeling bloated like in my pelvic area. Please help!!!