Why do I have abdominal pain after unprotected sex?

Hi doctor,

I had unprotected sex 19 days back. My period is always regular and my expected date was in the first week the following month. I had uneasiness and fatigue by the end of last month. Left side upper abdominal pain started a week back. It comes occasionally and goes on its own. Occasionally, the pain shifted to right side upper abdominal pain, then lower left side abdominal pain etc. My periods did not appear on the expected date. I did a pregnancy test yesterday, but the result was negative. Since yesterday, my appetite has reduced. After having dinner, my abdominal pain started increasing and it only stopped after I intentionally puked out half of the food I ate.

Today morning there was severe abdominal pain, periods like pain, and some drops of blood came out. After that I was revealed. Now the bleeding again stopped. Periods like pain persists and uneasiness after taking food. I wonder, whether I am pregnant and is that implantation bleeding. I read that the implantation bleeding occurs after seven to ten days of intercourse and before your missed period. In my case, there is a long gap and it is two days after the missed period. What could it be? I have no other symptoms of sore breast or nausea. Except, I feel fatigue especially in mornings and has become an early sleeper. I also have uneasiness after having food. No aversion or special interest to any food. But, not at all feeling hungry. Frequent periods like pain in the center lower abdomen. If there is a possibility of pregnancy, when can I again do a urine pregnancy test?