Have all the times you had sex since your son was born been in like the last week? If so it's too early to tell. I would call your DR in the am and inform him of what's going on and see what he recommends you do. Besides talking to your dr, all you can do is wait a few weeks then take a test!
There is a definite possibility. After you have a baby your body wants another baby in there, that's when it's easiest to get pregnant. You're very very fertile. Firstly you're supposed to wait six weeks after giving birth to have sex and secondly you need to go take a test! Good luck.