What Causes Delayed Periods And Vaginal Spotting?

I have a question me and my boyfriend have been having unprotected sex since he s been back from school he got here Dec 14 . I started my cycle on either the 21st or 22 . I know in fact of these day I do allow a three day window until I know I m for sure off I have a regular 7 day cycle meaning I was off by the 28th and we did continue to have inter course 31st and so on . he all uses pull out method not once did he leave in a week befor my start date we did continue unprotectedly we did stop when he left back on the 14th but now I didn t start my period on time I m 4 days late and now I m experiencing some spotting when I use the rest room I do see some blood but its only when I go pee . it started with spotting just enough for a liner now its showing more should I be worried ?!!!