Pregnancy conformation. Pls help me.

I have been suffering from secondary amenhorrea(since the last two months)and Now I have been assaulted sexually(this is the 3rd month) ..though I was wearing cotton clothing..we were watching a dance show and I didn't know there was someone behind me since there was a lot of crowd.I felt something's thirsting at my back near the anal area I turned around to check what was it only to find a guy behind me.he fled away from the scene .now when I came back home I saw his semen on my long shirt 3 spots 2 big and one small.it took around like 40-45 mins for me to get back to home.I rapidly went to the washroom to clean the area.now the problem is after like a day and a half I felt very light uterine cramps ..and now exactly on the 7th day I had what I think is implantation bleeding or maybe i am having my periods . I am really scared now.pls help me.