HI and thanks for using the forum.
You need to see your OB/GYN about this. This could be caused by an infection, a sensitivity to a soap or lotion, or an STD among other things. The only way to know for sure would be to see the OB/GYN and see what is going on. Untreated infectiions or STD's can cause issues with fertility later in life, so be sure to get checked out. Good luck.
Bridget
Make an appt with yr gyn asap could be a vd or the start of a yeast infect