Vaginal bleeding after sex

I'm concerned that I have been bleeding after I have sex. I read that this might be a symptom of chlamydia. The first time I noticed I bled was about three weeks ago. Although I'm also on the depo shot I didn't think much of it since the shot makes you spot. I maybe thought that was the reason I was bleeding. The bleeding lasted about a week then it stopped. About  a week later I started bleeding again, however I hadn't had sex since that last time. This time the bleeding lasted about only 4 days. I really don't know what to think of this. Then last night I had sex again and after I went to the bathroom I was bleeding not a lot but just a few spots. I don't know if I should be concerned about it being chlamydia? Has anyone ever experienced this same thing after sex. Or has anyone ever been diagnosed with chlamydia before?