Could Brown And Red Spotting Post Sex Indicate Implantation Bleeding?

Hi there, I am currently trying to conceive. I had the implant removed in January after 3.5 years. (it was removed late) The last two months I have had 37 and 35 days in my cycle. I used an ovulation calculator and according to that I was ovulating last Monday. My husband and I have had fairly regular sex throughout the month and I shouldn t be due on my period until next Monday (on a 35 day cycle). Last Tuesday I started with occasional bleeding when I went to the toilet. It was minimal and mainly brown. I continued to spot until yesterday. My husband and I had intercourse yesterday and I had fresh red blood immediately afterwards. Following that when I went to the bathroom there was no bleeding or spotting at all. I haven t felt very well; very emotional, sleepy and had horrible cramps on Thursday evening. Any ideas what could be happening? Maegan