I can't guess at an answer but have to say, please go see a doctor asap. It could be something simple, but best not to take chances with your health.
You may have a cyst on your ovary. It may be some inflammation, but it is most likely nothing to do with an std.
I used to get like that too. You're fu*king too hard and its just the back of your vagin@ being sore
THEN YOUR PARTNER IS SURFFERING FROM A SICKNESS SO PLS BOTH OF YOU SHOULD GO FOR CHECK UP