Ok I'm 18 (in a week) and worried. 

I have what I thought was old blood from the 8 missed periods due to the implant. I have had mine for about a year and a half. I have had no other pregnancy symptoms along with the discharge/blood ad some cramping. It's light but still heavy enough to use a tampon. I've been a little moody. But there have been no real significant changes. I have had unprotected sec recently but before we really got going, we decided to put a condom on (sorry gross I know) but aside from that no unprotected sex. Like I said it seen about 8 months since my last period. I take pregnancy tests often because my body likes to pretend its pregnant. I took one a couple weeks ago and it was negative. I guess I'm looking for some kind of reassurance that I'm not alone. Please let me know what you think and thank you in advance for your help.