hi there! mid cycle spotting can be caused due to various reasons...I had it one cycle..after every 7 - 8 days (each time around 3/4 days)..and my Dr said, it was due to my hormones going up and down ...but a lot of women have spotting around ovulation time and implantation bleeding(which is also spotting in some cases)..
that said, it might be caused due to polyps or cysts so it's best to get it checked by a qualified Dr..
good luck!
I had the same problem my last cycle so I did a lot of searching online and found that there are a lot of things that can cause this and most are not serious. I have a doctor's appointment in 2 weeks so I was just going to double check with my doctor at that time. If you are really worried about it, but too scared to go to the doctor, have you thought about calling your doctor's office to see if they have a nurse that will just give you their opinion over the phone about it?
It might not be anything to worry about at all but as from my experience, I was doing the same thing for over a year. It went from spotting to irregular bleeding inbetween periods, after sex and also when I'd do anything strenuous like yard work. Had it checked out and I had a polyp in the middle of my uterus. It has to be surgically removed but worth it. I got tired of bleeding all the time. Plus it can cause infertility, polyps can. I've been TTC for about 6 yrs now and they found this. :) Just mention it to your gyno, they can check you and tell you what's best. Good luck!! Keep us posted. Take Care!! :)