So I am a freshmen in high school and am on the cross country team. We started running four weeks ago and I have ran every day since then. I run from a range of only 1 mile to 3 miles. We started running on the 8th and I got my period on the 17th. It was really late because I normally start around the first of each month. It was also really really light! I could have probably worn one regular tampon all day and been fine! I never had really heavy ones but this one was my lightest yet! And it only lasted for 4 days ( my normal is 7!) This was not a real concern for me because I know that running can mess up your period sometimes. Well for the past day or so I have been getting this pain in my lower abdomen area where period cramps normally are, and they feel like period cramps but they are sharp. This morning I went on a mile long run and when I finished I had one of the sharp cramps. Later in the day I noticed a dark brownish discharge but blew it off. Well it continued all through the day. As it got later in the day it got more red in color. When I went to take a shower not to long ago it looked as if I had started my period! It was completely red in color and was not very evident on the toilet paper. It looks like normal period blood but its so close to my last period that it is kind of concerning. Should I just wait and see what happens? Or would it be best to maybe consult my doctor about it? Is this any cause for concern?

Any bit of help or advice would be amazing!

Thanks!