Stop injecting into your Junk. No matter what you have heard it wont make it bigger.....

On a serious note, you probably just had a HARD (no pun intended) ejaculation that caused a slight tear and even a 1/4 drop of blood with change the color enough to make it noticeble. Either use some lube or loosen your grip when choking the chicken or tell your significant other to not use her teeth.

I doubt it has anything to do with your cycle unless you are also seeing blood in your urine, then you need your kidneys checked.