There are a variety of causes of your symptoms.... but without a rash there are relatively few causes....
One thing this could be is something called scabies.... which is not an STD but which can cause very bad itching, and, eventually, a pretty bad rash.
the other thing that comes immediately to mind is pubic lice, commonly known as 'crabs', which IS often an STD.
for both of these conditions you would need a prescription to clear it up but really what you need is for someone to actually take a look at the area and try to get an idea of what may be going on.
if you do develop a rash THIS LINK HERE
lists all possible causes, and, just so you know, it is perfectly possible that this is simply early jock itch (tinea cruris) that has just not manifested as a rash yet as it is very itchy. any good antifungal cream or spray would be able to clear it up. you could ask your local pharmacists to recommend one to you if you wish to try to clear it up this way.
also, for the itch, you can take benadryl 25mg which will cut the itch quite a bit, though it may make you a bit sleepy.
I am standing by if you have any questions.