Is her boyfriend bigger than you are? Just kidding...
Yeah, resolve the issue with your girlfriend first. I'm sorry to say though that you have to think about your child too before jumping into another relationship if the one you are in doesn't work out. How is he going to react to another woman besides his mother? I know he's a little bit older, but it may be traumatic for him just the same...and confusing as hell.
"So tonight, when you're wondering what to say, or how you look, or whether or not she likes you, just remember, she is already out with you. That means she said yes when she could have said no. That means she made a plan when she could have just blown you off. So that means it is no longer your job to try to make her like you. It is your job not to mess it up."
-Hitch