I had that. It was also with a gradual onset…just crept up on me. I tried to push through it, and as a result, put myself out for a year and a half. Be careful what you do, and don't try to work through the pain, or there will be hell to pay.
There have been a few discussions on this type of injury on this site in the past. It could be you have an abdominal strain or hip flexor injury due to overuse. It could also be an injury to the pubic symphasis/rectus abdominus region. If it hurts to cough or the pain radiates out to one side of your groin, you know you are closer to being screwed.
You are in a very important stage of the game, here. You can play it safe, or pay the price. Mine was a sports hernia that I could have warded off had I been smart about it. Perhaps rtosh or others could lend some advice if you give some more info. Also, do a search on this site and check out the discussion at this link: