What Causes Blood On The Outer Vaginal Area But Not On The Tampon?

Hi, i'm fifteen years old and have been menstruating for 2 years now. So, i am quite familiar with using a tampon. My period is currently experiencing its third day. The flow is light but still deep red in color. The only symptom I am experiencing is lower back pain. I am worried that I have inserted another tampon without removing one. My vaginal area is slightly irritated and inserting the tampon is difficult without lubrication (this issue happens sometimes towards the end of my period anyway though). I removed the outter tampon with hopes of finding the "missing" one. (If there is one...) I also have tried to feel inside my vagina for the string but I could not feel one (i went about the length of the index finger). This makes me believe that there isnt a "missing" tampon up there because if there was one, I would have felt the string; Considering that Tampax Pearl tampon strings are rather long. I put a pad on about 30 minutes ago but there is still no blood on it. But, there is blood on the outter vaginal area, just not on the pad. I do not feel a tampon but im not sure if i have one inside me. Is there possibly a tampon up "up there"? Even though i checked?