I doubt you'd be pregnant enough to start showing that kind of symptom, or any kind of symptoms, yet.
The reason it takes approximately 10-14 days after you concieve to test for pregnancy - which is conveniently at the time of your expected period - is because it takes that long for the hcg to build up in your body. Women usually don't 'feel' pregnant prior to their missed period.
I'm sure you already are aware of this, but it sounds like this guy is promiscuous (he has another baby on the way, which means he has been having unprotected sex quite recently with someone else), you should be careful and protect your own body by making him (and all guys) wear a condom. Birth control is cheap - no reason not to use it.
Good luck!