Hi, I Had Unprotected Sex Twice On The 1st Jan

Hi, I had unprotected sex twice on the 1st Jan 2016. My first day of my last period was 18th December 2015. 1 week after unprotected sex, i started to get symptoms of swollen uterus and breast, cramps in the lower abdomen, lower back pains, and cramping down the right side of my leg and hip. Around 9DPO, I began to spot with light pinkish blood for 1 day. Then 4 days after spotting, my periods were due on the 15th Jan, I only bled for one day with lots of dark red tissues coming out , I've never had that before. I've never gotten a 1 day cycle before. In between these times I've taken a Home pregnancy test, all results were negative except for one came up faint positive then disappeared. Around the 17th Jan, I bled a little for a few hours then it stopped. Everytime I wiped with a tissue there would be watery pinkish blood. On 18DPO, I decided to take a pregnancy test when still slightly bleeding pink, and result said I'm not pregnant, my hcg levels were a 2. It's week 3, I got a little cramping in the lower abdomen and lower back felt like my periods were coming on, but my next period is on the 12th Feb I believe. Yesterday 26th January, I began to feel nauseas, so i had to have a rest for a while. Can you please tell me why I may be having these symptoms? Or did I have a miscarriage ?