Bleeding 18 days post D&C

So I had missed miscarriage. I took the pills to help me pass starting July 17th I had to take the pills three times and I ended up getting a D&C due to tissue left behind. I had a D&C June 3th I had bleeding until July 2nd. I went to my OB on July 14th for post D&C check she never checked me just asked me what I was going to do for birth control and if I had stopped bleeding. Now I'm 18 days post D&C and I'm having light red bleeding and some mild cramps. Is this normal or should I call my OB? She told me wouldn't get my period for a month. I told her when I went on Tuesday I felt like I was going to get my period. I have cramps and my chest are sore. I will admit I did start having sex again July 3rd but I haven't had sex since Tueday. So could that have something to do with it? I know I should have had sex but I only had a piece of tissue left and I was cleared to go back to work the next day which requires heavy lifting and such.