You have nothing to worry about, from what i can see it appears you have no fertility problems.... you are simply not pregnant again instantly....so many things affect this. You are so so young, so you have so many years ahead of you and all the time in the world. At least you have your baby boy - if you search online you will see the absolutely huge community of non fertile suffers for varying reasons, degrees, accidents and illnesses. Spend an hour reading some blogs and you will soon be very very very grateful that you have your baby boy and this might put things into perspective for you a bit more --- which should minimise your urgency which in turn minimises your stress and thus improve your chances while also being aware if just how lucky you really are!!!!! 6 months is not a long time in the slightest to be trying so it is very early days for you - think about people who try for years and years... even the most fertile and healthiest people may not get pregnant in such a short amount of time. I wish you the best of luck on expanding your family but just keep the above in mind. :)