MC in February!

My S/O & I had a miscarriage at 19 weeks on February 20th. Since then we haven't been preventing it but haven't actively been trying either. One of those if it happens we will be happy things!! I didn't track my ovulation this month so I'm not sure if or when I ovulated. AF was due August 23rd but never showed. I am NEVER late. Usually a day or 2 early if anything!!. I have taken 2 pregnancy test , 1 on Aug 23 and the 2nd one today! They both came back negative. For 2 weeks now I have had some lower stomach cramps, lower back pain, boobs are swollen, nipples sore& heartburn/indigestion! Has anyone else had this happen before??