When to take pregnancy test with irregular period ?

It is been almost 4 months after My bf fingered me. That month, my period was 10 days late, I got my period every month but also have some pregnancy symptoms.... I was so streees out from that time. And Now, i decide to take a test but since i have my period every month ( light period ), I don't know when to take it. My next period should be in a couple days... January 15 to 17. Help me out guys... 

I need to know when to take the test.....